Recent Questions - Chemistry Stack Exchange most recent 30 from chemistry.stackexchange.com 2023-11-30T05:43:46Z https://chemistry.stackexchange.com/feeds https://creativecommons.org/licenses/by-sa/4.0/rdf https://chemistry.stackexchange.com/q/177996 -2 To mix sodium borohydride and boric acid [closed] Monalisha Chutia https://chemistry.stackexchange.com/users/140154 2023-11-30T00:23:18Z 2023-11-30T00:23:18Z <p>What concentration of 50ml boric acid should I make to mix with 50ml sodium borohydride, so that the total concentration is 1mM? What should be the individual concentrations of the solutions to make a 100ml solution of total concentration 1mM?</p> https://chemistry.stackexchange.com/q/177995 0 How do I explain that voltage decreases when increasing the concentration of the cathode in a voltaic cell? Night https://chemistry.stackexchange.com/users/140152 2023-11-29T23:11:06Z 2023-11-30T01:54:52Z <p>I just finished a lab experiment in which I built a voltaic cell with copper (II) sulphate and zinc sulphate. My experiment was to identify the correlation between the concentration of copper (II) sulphate and the voltage generated.</p> <ul> <li>I started with a 200 ml solution of 0.5 molar copper (II) sulphate and a 200 ml solution of 0.5 molar zinc sulphate solution (which is constant).</li> <li>I measured the voltage of the cell at 0.5 M for both and I got about 1.088 V.</li> <li>I added 1g of copper (II) sulphate anhydrous (crystal) to the copper (II) sulphate solution after every trial (which effectively increases the concentration of copper (II) sulphate (the cathode)) but I realized that each time I did that the voltage <strong>decreased</strong>. For context, I added 1g 18 times and I ended up with a voltage of 1.029 V.</li> </ul> <p>So <strong>TLDR</strong>, increasing the concentration of copper (II) sulphate (the cathode) <strong>decreased</strong> the voltage of my voltaic cell instead of increasing it.</p> <p>A few other students in my class did the same experiment (slight differences in methodology) and their voltage increased, which supports my original hypothesis of voltage increasing with concentration and also supports the Nernst equation (pretty sure).</p> <p>Can anyone PLEASE help me understand why the voltage <strong>decreased</strong> when I <strong>increased</strong> the concentration of copper (II) sulphate?</p> https://chemistry.stackexchange.com/q/177993 1 Iodine solution concentration Ance https://chemistry.stackexchange.com/users/140148 2023-11-29T20:19:54Z 2023-11-29T21:54:14Z <p>I am planning to make 1L of 0.005M iodine solution from KI and I2. I have found instructions that say to use 2 g of KI and 1.3 g of I2 but no explanation why exactly this particular amount. I also found that iodine solution concentration will be the same as the concentration of the added I2, again no explanation.<br /> Could someone please explaine the calculations behind this? What and how affects the final concentration? Since there is a reaction happening (KI + I2 = KI3), I am a little confused.</p> https://chemistry.stackexchange.com/q/177992 -1 Substituent Priority user140138 https://chemistry.stackexchange.com/users/140138 2023-11-29T17:01:23Z 2023-11-29T17:01:23Z <p>I'm trying to do an oxymercuration/demercuration reaction but I can't figure out which side of my alkene is more substituted. I believe it should be the side with the methyl group. Could someone explain to me why one side would be more prone to nucleophilic attack than another?</p> <p><a href="https://i.stack.imgur.com/gzp2L.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gzp2L.png" alt="enter image description here" /></a></p> https://chemistry.stackexchange.com/q/177991 -2 Can we break down CO2 to solve climate change? J Kilvington https://chemistry.stackexchange.com/users/140137 2023-11-29T16:31:39Z 2023-11-30T01:24:35Z <p>I'm not past basic college chemistry class myself, but it seems to me that there may be an eloquent solution to eliminate CO2 levels in the environment:</p> <p>Can we not separate the carbon (through electrolysis?) from the molecule resulting in ozone. Then separating the two oxygen. Splitting airborne CO2, probably densely sequestered, leaving a pile of carbon and (liquid??) Oxygen.</p> <p>Depending upon scale this could mitigate CO2 levels.</p> <p>This is beyond my pay grade, but it has been on my mind lately without complete solution to the puzzle.</p> https://chemistry.stackexchange.com/q/177990 -2 How dangerous is Naphtha? Rocketmagnet https://chemistry.stackexchange.com/users/80659 2023-11-29T16:27:48Z 2023-11-29T16:27:48Z <p>According to a <a href="https://download.basf.com/p1/000000000030052956_SDS_GEN_US/en_US/Naphtha_000000000030052956_SDS_GEN_US_en_2-0.pdf" rel="nofollow noreferrer">safety datasheet of Naphtha</a>, it's fairly dangerous stuff (including genetic defects). But, as they say, the dose makes the poison, just how much dose should I be worried about?</p> <p>Currently, we use a silicone adhesion primer (<a href="https://nusil.avantorsciences.com/assetsvc/asset/en_US/id/29204353/contents/en_us_sds_nusisp-270.pdf" rel="nofollow noreferrer">SP-270</a>), which is dissolved in Naphtha. We use it in a fume cupboard, brushing it onto small metal parts with a tiny brush. The Naphtha evaporates pretty quickly, before we remove the metal part from the fume cupboard. We don't wear gloves.</p> <p><strong>Questions:</strong></p> <ul> <li>Does this method of handling Naphtha sound unsafe?</li> <li>How much exposure to Naphtha is necessary before I'm likely to experience any of the nasty effects? If I accidentally touch the brush, should I be worried? Or do I need to swim in it to get an effect?</li> </ul> https://chemistry.stackexchange.com/q/177984 -1 Do Vitamins Occur in Different Forms in Foods? [closed] Holly https://chemistry.stackexchange.com/users/140125 2023-11-29T09:57:24Z 2023-11-29T09:57:24Z <p>Vitamin C, for example, can occur in the form of ascorbic acid, calcium ascorbate, sodium ascorbyl phosphate etc. My question is, do vitamins occur in different states in food?</p> <p>A wholefood vitamin C supplement made from dried, powdered acerola cherries contains 25% vitamin C. But is that particular form of vitamin C? My guess would have been D-ascorbic acid, but when I asked the manufacturer I was told &quot;this is a non-acidic form and as the vitamin C occurs in food, it does not have a chemical name&quot;. This doesn't sound right to me, but I'm not a chemist!</p> <p>(I think I'm right in saying D-ascorbic acid is the form in which vit C occurs naturally in fruits, whereas L-ascorbic acid is synthetically produced)</p> <p>Thanks</p> https://chemistry.stackexchange.com/q/177983 0 Why potassium carbonate breaks glass when heated? Clinfosfito https://chemistry.stackexchange.com/users/140123 2023-11-29T09:37:28Z 2023-11-29T12:19:20Z <p>I have been studying about desiccants for a while and testing some inorganic salts, including calcium chloride, sodium sulfate and potassium carbonate. When they get enough moisture from air, I dehydrate them by heating up in a borosilicate glass, and during the process everything looks fine for all, but with potassium carbonate the glass always breaks after 1 or 2 cycles, and I don't know why. It should be clear that this doesn't happen with the other salts even after more than 15 cycles so far, and it takes several minutes or even hours after the glass cools down (I didn't even watch the exact moment when this happens). So I will be grateful for your answer and any suggestions of what material could be more appropriate for the task</p> https://chemistry.stackexchange.com/q/177977 2 What is the ionic conductivity of the hydroperoxide ion? HiddenBabel https://chemistry.stackexchange.com/users/102711 2023-11-29T02:30:02Z 2023-11-29T02:38:21Z <p>Hydrogen peroxide is supposed to dissociate as</p> <p><span class="math-container">$$\ce{H2O2 &lt;=&gt; H+ + HO2-}$$</span></p> <p>But I can't find a source for the conductivity, <span class="math-container">$\lambda$</span>, of the hydroperoxide anion <span class="math-container">$(\ce{OOH-}$</span> or <span class="math-container">$\ce{HO2-})$</span> on Google.</p> https://chemistry.stackexchange.com/q/177975 0 When you do dehydrohalogenation of 1° alkyl halides, do you use a strong base or sterically hindered base? Jordan https://chemistry.stackexchange.com/users/140109 2023-11-29T02:01:24Z 2023-11-29T08:20:15Z <p>I know when do you dehydrohalogenation of <strong>2° alkyl halides</strong>, you can do either a strong base like <strong>KOCH2CH3</strong> to get the most substituted product or a sterically hindered base like <strong>t-butoxide</strong> to get the less substitued product. However, I do not understand whether you would use the strong base or sterically hindered base for <strong>1° alkyl halide</strong> because there are not two options here.</p> https://chemistry.stackexchange.com/q/177974 -3 What are these plates in LixC6? Fedor Pasynkov https://chemistry.stackexchange.com/users/139783 2023-11-29T01:11:36Z 2023-11-29T12:57:05Z <p>I'm completely new to chemistry. I can’t personally figure out the basic issues myself, so I’m asking for your help. I became interested in how lithium-ion batteries generally work. As a result, I came to what is the most used material for the anode. This is LixC6. But I don't understand what its structure means, i.e. How do we even understand this? Why are there 3 dies here? What is 'x' in LixC6? Can you explain please. If the question is not clear enough, then let me know, because I really don’t know much about chemistry and I can ask quite stupid questions. <img src="https://i.stack.imgur.com/jfcbK.png" alt="1" /></p> <hr> <b>References</b> <br> Image Source - Electronic structure ‘engineering’ in the development of materials for Li-ion and Na-ion batteries. <a href="https://www.researchgate.net/figure/Operation-of-the-commercial-Li-x-C-6-Li-Li-1-x-CoO-2-battery_fig1_313266821" rel="nofollow noreferrer">Link</a> https://chemistry.stackexchange.com/q/177972 -2 Ammonia (NH3) vs Ammonia Nitrogen (NH3-N) Kuhrta https://chemistry.stackexchange.com/users/136569 2023-11-28T23:25:31Z 2023-11-29T23:48:17Z <p>I've been looking into chloramination (chlorine &amp; nitrogen reactions) and noticed many papers either reference Ammonia (NH3) or Ammonia-Nitrogen (NH3-N), seemingly interchangeably.</p> <p>Is the hyphenation simply nomenclature for &quot;<em>we are only interested in measuring the nitrogen component of ammonia</em>&quot; or does NH3-N present as a distinct compound in water treatment?</p> <p>For example, if a paper provides a Cl2:N Ratio of NH3, is this equivalent to a Cl2:N ratio of NH3-N?</p> <p>Note: Asking in parallel to my <a href="https://chemistry.stackexchange.com/questions/177971/what-is-meant-by-as-cl2">'as xxx' question</a>. Posting separately to avoid convolution.</p> https://chemistry.stackexchange.com/q/177971 0 What is meant by 'as Cl2' Kuhrta https://chemistry.stackexchange.com/users/136569 2023-11-28T22:43:12Z 2023-11-30T00:02:06Z <p>I feel like I'm over thinking this one, but think I need a confirmation (and quantified example) to put my confusion to bed. I'm more a mechanical than chemical background but trying my best.</p> <p>I really get stuck on papers measuring concentrations 'as XXX' when the 'XXX' is only a component of the compound.</p> <p>Example 1: Hypochlorous Acid (HOCl) has a weight of 52.457 g/mol, while chlorine weighs 35.45 g/mol. Thus, the chlorine weight fraction would be ~67.5%. As this would be measured as Cl<strong>2</strong> would we then halve the above weight fraction as we only have a single molecule of chlorine.</p> <p>Example 2: If we add 1mol (143g) of Calcium Hypochlorite to make 1-litre of solution. <a href="https://i.stack.imgur.com/qLTao.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qLTao.png" alt="Calcium Hypochlorite to Hypochlorous Acid" /></a></p> <p>We would create 2mol (105g) of Hypochlorous Acid, which includes 2mol of Cl (aka 1mol of Cl2) weighing 70.9g. As we are interested in chlorine, would we express this as a measurement of HOCl 70.9g/l &quot;<em>as Cl2</em>&quot;? Or do we consider the entire mass of hypochlorous acid?</p> https://chemistry.stackexchange.com/q/177970 -3 35% H202 no stabilizers storage [closed] Mandi https://chemistry.stackexchange.com/users/140104 2023-11-28T21:20:10Z 2023-11-28T21:20:10Z <p>Bottle is currently unopened&amp;in my freezer.I don't need to use it all so when I put the lid back on will I need to worry about pressure building up in the bottle?(lid is not vented nor is the bottle) And 1more question when I dilute what I need to 3% do I really need to put it in HDPE bottle? Thanks for help!</p> https://chemistry.stackexchange.com/q/177969 1 Electrochemical double layer formation Mäßige https://chemistry.stackexchange.com/users/120038 2023-11-28T21:13:19Z 2023-11-28T21:13:19Z <p>I was revisiting some of my notes about the electrochemical double layer but I have some doubts, and even the textbook of Bard and Faulkner could not really help.</p> <p>In electrochemical systems, at the potential of zero charge (PZC) there is no charge on the electrode surface and therefore no electrochemical double layer as I understand it (it is the maximum of the following graph, potential vs surface tension):</p> <p><a href="https://i.stack.imgur.com/hS4zk.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hS4zk.jpg" alt="enter image description here" /></a></p> <p>Using the PZC now as our reference point where there is no double layer, if we shift the applied potential on the electrode to more positive values than the PZC (assume there is no faradaic reaction, only capacitive effects) of course, a double layer forms. Now my question is:</p> <p>If the applied potential is more positive than the PZC, does that mean, that the electrode is positively polarized due to the applied potential and anions are moving closer to the electrode surface? Or if the applied potential is more negative than the PZC the electrode is negatively polarized and more cations are near the electrode, or is a metal electrode generally positively polarized?</p> <p>So does the “sign” of the electrode’s charge have something to do with the potential that we apply, or is the EDL independent of the applied potential (should be Helmholz assumption)?</p> https://chemistry.stackexchange.com/q/177967 -4 Order of Acidic Strength between 3-Fluorophenol, 3-Chlorophenol, 3-Bromophenol and phenol . Also explain why? [duplicate] Sharie https://chemistry.stackexchange.com/users/140088 2023-11-28T19:49:01Z 2023-11-28T19:49:01Z <p>Show me where I'm wrong??? Here we are going to find acidic strength ,so -I effect of halogen will consider rather than +M effect of it. As negative Inductive power i.e.-I power of Fluorine is higher than other halogens so Order of Acidic Strength between a)3-Fluorophenol, b)3-Chlorophenol, c)3-Bromophenol and d)phenol</p> <p>should be d&lt;c&lt;b&lt;a</p> <p>Also we know that Mesomeric effect is not applicable at meta position.</p> <p>Show me the correct order of Acidic Strength.</p> https://chemistry.stackexchange.com/q/177966 0 Ca(OH)2 not dissolving even as much as it should Shaun Nagy https://chemistry.stackexchange.com/users/140101 2023-11-28T18:24:48Z 2023-11-28T18:24:48Z <p>according to solubility charts Ca(OH)2 should dissolve at 20-25 oC at about 1.6g per litre. I have tried 0.8, 0.4 and 0.2g in 500ml and even the 0.2 does not completely dissolve, even left overnight. (in fact I would say most of it is undissolved on the bottom of the flask). rm temp is around 19-20oC, using lab grade ca(OH)2 and distilled water Any thoughts/suggestions?</p> https://chemistry.stackexchange.com/q/177964 -2 Why the Stoichiometric Coefficients are raised to the power of the concentration of the respective reactant? [duplicate] Shashwat https://chemistry.stackexchange.com/users/138944 2023-11-28T17:31:03Z 2023-11-29T20:08:24Z <p>While studying Chemical Kinetics, a question popped up in my mind that in Law of Mass Action, why the Stoichiometric Coefficients are raised to the power of the concentration of the respective reactant? What is it's significance?</p> https://chemistry.stackexchange.com/q/177960 0 When C2 axis of symmetry is present then is the compound meso? Garv Chaudha https://chemistry.stackexchange.com/users/129185 2023-11-28T15:27:34Z 2023-11-28T15:27:34Z <p>If suppose a compound has C2 axis of symmetry then is it confirmed that the compound will be meso or it can have an enantiomeric pair? And which of following conditions are sufficient enough to declare a compound meso:- Plane of symmetry, Centre of symmetry, axis of symmetry and alternate axis of symmetry?</p> https://chemistry.stackexchange.com/q/177959 -2 Ammonia floor cleaners [closed] DEVON https://chemistry.stackexchange.com/users/140093 2023-11-28T14:49:12Z 2023-11-28T14:49:12Z <p>0</p> <p>Can I use an Ammonia based floor cleaner on floors that were previously washed with Bleach? will that produce a reaction that will lead to Chloramine gas or does that only happen if the 2 liquids are combined together?</p> https://chemistry.stackexchange.com/q/177952 1 Carrying out electrolysis of very dilute NaCl for a long time Freeby Freeby https://chemistry.stackexchange.com/users/134331 2023-11-28T10:30:33Z 2023-11-29T14:00:36Z <p>I find a similar question in stack exchange (<a href="https://chemistry.stackexchange.com/questions/164953/what-will-happen-if-the-electrolysis-of-brine-takes-place-for-a-long-time">What will happen if the electrolysis of Brine takes place for a long time?</a>), yet it does NOT seem to respond to my question.</p> <p>Suppose I am electrolysing a very dilute sodium chloride solution. At the anode, the hydroxide ions will get oxidised into oxygen gas, while at the cathode, the hydrogen ions will get reduced into hydrogen gas.</p> <p>Now, if I leave the set-up ongoing for a long time, is it true that all the water will be consumed and I will obtain a beaker of molten sodium chloride (given that heat is constantly provided)?</p> <p>My lecturer pointed out that this is impossible to happen. When a lot of water is consumed, then I will obtain concentrated sodium chloride solution, namely brine. So, at the anode, the chloride ions will get oxidised to give chlorine gas, while at the cathode, the hydrogen ions are still reduced to give hydrogen gas.</p> <p>Can anyone provide me with the whole picture of the case provided by me? Please be noted that I am talking about very diluted NaCl solution instead of brine.</p> https://chemistry.stackexchange.com/q/177951 1 How can we prevent retrogradation of starch? Aqib Mehmood https://chemistry.stackexchange.com/users/140076 2023-11-28T07:06:44Z 2023-11-28T14:45:47Z <p>Are there any additives which can prevent <a href="https://en.wikipedia.org/wiki/Retrogradation_(starch)" rel="nofollow noreferrer">retrogradation of starch</a>? I have prepared 13% of starch solution along with 2% of NaCl. The results were bit better. The synthesized gel was flowable with some bubbles inside it, perhaps 2% of salt was more than enough. Coming back to my question, are there any better substances which can be used for this purpose?</p> https://chemistry.stackexchange.com/q/177950 0 Is there a supercritical state for ice? suse https://chemistry.stackexchange.com/users/63035 2023-11-28T05:09:15Z 2023-11-28T16:38:57Z <p>I know there is such a thing as a supercritical fluid, where the vapor and liquid phases are indistinguishable, but is there such a thing as a supercritical state for ice? Another way of asking this is: what happens to ice when it is subjected to pressures above the critical pressure, 217.75 atm, in the case of water?</p> https://chemistry.stackexchange.com/q/174749 1 Comparing Succesive Ionisation Energies Charles Dickens https://chemistry.stackexchange.com/users/135336 2023-07-01T11:18:55Z 2023-11-29T15:06:50Z <p>I am trying to understand successive ionisation energies. In particular, an explanation for why the second ionisation energy is greater than the first ionisation energy. I'm looking for a clear and concise explanation.</p> <p>The common explanation is that it's harder for an electron to be removed from a cation than the atom or that the second electron feels a greater nuclear charge. However, these explanations do not satisfy me.</p> <p>For starters, How can the nuclear charge be greater for the second electron when the number of protons within the nucleas remains unchanged. Assuming both the first and second electrons are on the same energy level, they experience the same amount of shielding from inner electrons. So it seems to me, both electrons feel the same nuclear charge. I can see the second electron, perhaps feeling repulsion from the first that results in less nuclear charge. Would this then be correct?</p> <p>I don't particularly understand the explanation about it being harder to remove an electron from a cation. The way I see it, is that the atomic radius decreases when the first electron is removed, meaning the second electrons feels more electrostatic attraction from being closer. Is this explanation sufficient? Could someone please provide a clear explanation for this?</p> https://chemistry.stackexchange.com/q/165389 4 Can a spontaneous reaction have zero or negative activation energy? Karan https://chemistry.stackexchange.com/users/114591 2022-05-26T09:46:54Z 2023-11-28T19:26:48Z <p>Is it possible for a <em>certain</em> spontaneous reaction to have zero or negative activation energy?</p> <p>My high school teacher explains that it shouldn't be possible since it breaks the Arrhenius equation, namely the Boltzmann factor</p> <p><span class="math-container">$$\exp\left(\frac{-E_\mathrm{a}}{RT}\right),$$</span></p> <p>which gives the fraction of molecules having <span class="math-container">$E_\mathrm{kin} &gt; E_\mathrm{a}.$</span> So, instead of putting in <span class="math-container">$E_\mathrm{a} &lt; 0$</span>, we will just say the Boltzmann factor is equal to 1. The Boltzmann factor just doesn't make sense for a negative <span class="math-container">$E_\mathrm{a}$</span> as <span class="math-container">$E_\mathrm{kin}$</span> cannot be negative.</p> <p>Instead of saying it breaks the factor, should we not just say that the factor is <em>undefined</em> for negative energy values and that <span class="math-container">$E_\mathrm{a}$</span> can be zero or negative?</p> <p>Edit- so people are commenting on the question and I am very thankful. But I also want to know that if this was a test question with a simple true or false answer, would you say that <span class="math-container">$E_a$</span> can be <span class="math-container">$&lt;0$</span> or not?</p> https://chemistry.stackexchange.com/q/147240 -2 Can Gibbs free energy determine whether a reaction is endothermic or exothermic? Aniruddha https://chemistry.stackexchange.com/users/39388 2021-03-07T12:30:15Z 2023-11-28T17:56:40Z <p>In the solution of a problem on thermodynamics, it is mentioned that:</p> <blockquote> <p><span class="math-container">$\therefore$</span> Reaction will be endothermic if <span class="math-container">$\Delta G^{o}&gt;0$</span></p> </blockquote> <p>In my knowledge, the Gibbs free energy is usually used for determining the spontaneity of a given reaction. So, this statement is new to me.</p> <p>Please clarify how we can determine whether a reaction is endothermic or exothermic with Gibbs free energy.</p> <p><a href="https://i.stack.imgur.com/P9ZRW.jpg" rel="nofollow noreferrer">Here</a> is the link to the problem for anyone interested.</p> https://chemistry.stackexchange.com/q/104950 4 How to derive the relation between gibbs energy and equilibrium constant? pranjal verma https://chemistry.stackexchange.com/users/62732 2018-11-28T11:37:34Z 2023-11-29T07:41:52Z <p>I want to understand the derivation between gibbs energy and equillibrium constant <span class="math-container">$$\Delta G=\Delta G^o+RT\ln Q?$$</span> I have seen a similar post on CSE <a href="https://chemistry.stackexchange.com/questions/6827/derivation-of-relationship-between-equilibrium-constant-and-gibbs-free-energy-ch">Derivation of relationship between equilibrium constant and Gibbs free energy change</a> which seems to be incomplete and still confusing so I am again asking this question.</p> <p>The derivation that was written in the post was as follows:</p> <blockquote> <p>Using the fundamental equations for the state function (and its natural variables):_ <span class="math-container">$$dG=-SdT+VdP$$</span> <span class="math-container">$$V=(\dfrac {\partial G}{\partial P})_T$$</span> <span class="math-container">$$\bar G(T,P_2)=\bar G(T,P_1)+\int_{P_1}^{P_2}\bar V dp$$</span> Here <span class="math-container">$\bar x$</span> represents molar <span class="math-container">$x$</span>, i.e. <span class="math-container">$x$</span> per mole <span class="math-container">$$\bar V=\frac {RT}{P}$$</span> <span class="math-container">$$\bar G(T,P_2)=\bar G(T,P_1)+RT \ln\frac {P_2}{P_1}$$</span> Defining standard state as <span class="math-container">$P=1\text{bar}$</span> and <span class="math-container">$\bar G=\mu$</span> <span class="math-container">$$\mu(T,P)=\mu^o (T)+RT\ln \frac{P}{P_o}$$</span> consider the general gaseous reaction <span class="math-container">$aA+bB\rightarrow cC+dD$</span> <span class="math-container">$$\Delta G=(c\mu_C+d\mu_D-a\mu_A-b\mu_B)$$</span> for "unit progress" in reaction. Using <span class="math-container">$\mu_i=\mu^o_i+RT\ln \frac{P_i}{1bar}$</span> <span class="math-container">$$\Delta G=(c\mu^o_C+d\mu^o_D-a\mu^o_A-b\mu^o_B)+RT\ln \frac{P_C^cP_D^d}{P_A^aP_B^b}$$</span> <span class="math-container">$$\Delta G=\Delta G^o+RT\ln Q$$</span></p> </blockquote> <ol> <li>I know the relation between Gibbs free energy,Enthalpy,Entropy and Temperature as <span class="math-container">$$G = H - TS$$</span> how is the relation <span class="math-container">$dG=-SdT+VdP$</span> derived from the above formula?</li> <li>Why do we take a path where Entropy and volume are constant in the equation <span class="math-container">$dG=-SdT+VdP$</span> as in a chemical reaction both volume and entropy can change?</li> </ol> https://chemistry.stackexchange.com/q/94101 11 What do the six polymorphs of chocolate look like? spraff https://chemistry.stackexchange.com/users/10112 2018-03-26T22:37:05Z 2023-11-30T02:13:46Z <p>Today I learnt that chocolate tempering works by controlling the temperature to ensure the crystals set to one (type V) of the six polymorphs.</p> <p><a href="https://i.stack.imgur.com/67qVb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/67qVb.png" alt="enter image description here"></a></p> <p>What do these polymorphs actually look like? By that I mean: what is the crystal structure? Also, what gives type V its properties?</p> https://chemistry.stackexchange.com/q/63142 1 Why the current of double layer charging is independent of potential? QQQ https://chemistry.stackexchange.com/users/37794 2016-11-23T12:48:51Z 2023-11-28T19:58:11Z <p><em>i-V</em> curve of double layer charging has a rectangular shape. Why when increasing or decreasing the voltage, the current remains constant?</p> <p>Or I can ask, how the double layer structure is changing by varying the applied voltage?</p> https://chemistry.stackexchange.com/q/54826 5 Why does CO2 diffuse through a butyl rubber membrane more readily than air? R. Gold https://chemistry.stackexchange.com/users/31837 2016-07-11T23:08:00Z 2023-11-29T16:01:55Z <p>I am a cyclist, and not a chemist. When I or my cycling buddies get a flat tire out on the road, after removing the offending sharp object (if any) remaining in the tire, we will typically replace the punctured butyl rubber inner tube with a new one, and then inflate the tire using a $\ce{CO2}$ cartridge.</p> <p>Inflating the tire in this way takes less than a second to bring the pressure up to 120 psi. At home, naturally, we fill our tires with air rather than a $\ce{CO2}$ cartridge, using a floor pump.</p> <p>When we fill our tire with an air pump the tire remains inflated for several days. But after filling it with $\ce{CO2}$, the tire is severely flat again by the next morning. $\ce{CO2}$ clearly diffuses through the butyl membrane very much more rapidly than air, even though $\ce{CO2}$ is a larger molecule than either $\ce{N2}$ or $\ce{O2}$. Is it the shape of the molecule? Or its chemical properties?</p>