Questions tagged [homework]

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240 views

Isomers of co-ordination compounds

Does $\ce{[Co(H2O)3Br3]}$ show geometrical and optical isomerism? According to me $\ce{Co}$ should be $\mathrm{sp^3d^2}$ hybridised giving an octahedral geometry. It is of the form $\ce{Ma3b3}$ type. ...
2
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1answer
7k views

Hybridization of tetraamminecopper(II) sulfate

$\ce{Cu^2+} $ has 9 electrons and a d-orbital and is almost completely filled (except 1 electron vacant) and $\ce{NH3}$ donates an electron eventually forming $\mathrm{sp^3}$ hybrid orbitals. But it ...
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2answers
1k views

Plot Binary Eutectic from Temperature of Melting and Enthalpy

I'm a little confused about plotting a binary eutectic diagram (temperature vs mole fraction), and finding the eutectic point. I understand the eutectic point is the lowest temperature that a mixture ...
3
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2answers
257 views

Equilibrium constant. Can it be reached?

Consider the reaction below: $$\ce{A + B <=> C}$$ Suppose that the equilibrium constant for this reaction is $K = 10$. I then prepare a reaction vessel with volume of $1~\mathrm{dm^{-3}}$ ...
3
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1answer
2k views

Markovnikov's addition to halogenated alkene?

The justification or rather intuition behind Markovnikov's rule is the stability of intermediate carbocation. The more substituted the carbocation the more stable the product. But based on this ideas ...
1
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1answer
24k views

How to calculate the concentration of all relevant species in a buffer of a given pH?

You prepare $1.0~\mathrm{L}$ of a $0.25~\mathrm{M}$ acetic acid solution with a final $\ce{pH}$ of $6.0$. What are the molar concentrations of all relevant acetic acid species ($[\ce{HA}]$ and $[\ce{A-...
3
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1answer
3k views

Application of the Arrhenius equation to a parallel reaction

I'm struggling with this homework question: "For a parallel reaction A goes to B with rate constant $k_1$ and A goes to C with rate constant $k_2$, you determine that the activation energies are 71.9 ...
2
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2answers
369 views

Significant Figures in almost-scientific notation

For a homework assignment on significant digits, I have to find the number of significant digits in the number $0.40 \times 10^3$. I know that in scientific notation, the number of significant digits ...
2
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2answers
2k views

When is rotation around double bonds to form cis-trans isomers allowed?

The Rhodopsin molecules in the retain contain a derivative of vitamin A called cis-retinal (Figure 6). On exposure to light, cis-retinal becomes an isomer called trans-retinal (Textbook Question). ...
2
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2answers
1k views

Using sigfigs when measuring with an instrument with marks other than powers of ten?

If an instrument does have markings that are powers of ten, then finding the precision of the instrument is easy. For example, if a graduated cylinder had markings for every 0.1mL, or every mL, or ...
1
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1answer
26k views

Calculating the molar mass of a solute from freezing point

A $\pu{4.305 g}$ sample of a nonelectrolyte is dissolved in $\pu{105 g}$ of water. The solution freezes at $\pu{-1.23^\circ C}$. Calculate the molar mass of the solute. $k_f$ for water is $\pu{1.86 C/...
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1answer
894 views

Molarity to Percent, Mole Fraction, Molality

I have a series of questions similar to the following. I want to make sure I do this correct before I do the others. I am in need of a hint. ...
5
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3answers
5k views

Why do the trends in reactivity not apply for francium?

Why is francium not included in the reactivity series? Why is potassium considered more reactive than francium? I know that reactivity increases down the group! But why does it not apply here?
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1answer
8k views

When Z>1 are repulsive forces dominant or are attractive forces dominant?

According to PVreal = ZRT If z >1 repulsive forces are dominant or are attractive forces? Different teachers are telling contradictory answers and after referring a few books, I have become more ...
4
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3answers
3k views

Identifying an unknown compound(w/ NMR/IR)?

I need some help identifying the following unknown compound. Any suggestions or hints regarding the possible compound would be highly appreciated. So far I am thinking the broad peak on the IR is an ...
3
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2answers
12k views

Determining if reaction is endothermic or exothermic using equilbrium constant

For the following reaction: $$\ce{W_{(s)} + 4 Br_{(g)} <=> WBr4_{(g)}}$$ At 900 K, $K_\mathrm{p}=100$ and at 2800 K, $K_\mathrm{p}=5$. At higher temperatures, the equilibrium has shifted ...
3
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3answers
2k views

Solubility Product and Buffers

I've been assigned a homework and the question looks like this :- The ionization constant of benzoic acid is $6.46 \times 10^{-5}$ and solubility product for silver benzoate is $2.5 \times 10^{-13}$...
3
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1answer
2k views

∆Enthalpy of diatomic molecules

Question: The reaction between hydrogen and oxygen to yield water vapor has $\Delta{}H^\circ = -484~\mathrm{kJ}$. How much $PV$ work is done, and what is the value of $\Delta{}E$ in kilojoules ...
2
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1answer
2k views

Absolute configuration when hydrogen (lowest priority group) is in the plane of the page (and not a wedge or dash)

I have learnt that: Our absolute configuration is R(if clockwise) or S(if anticlockwise) when we rank the priorities, when the hydrogen (or other lowest priority group) is at the rear i.e. into the ...
2
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1answer
318 views

What is the product of two irreducible representations on the character table?

Let's say the direct product of $\ce{A1}$ and $\ce{B1}$ on $\ce{C}_{2v}$ character table, what is the direct product of the two for water molecule? or for any other instance in general, what does the ...
2
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1answer
164 views

How is the Rate Law of a reaction measured?

What is Rate Law of the reaction below?$$\ce{4 HBr + O2 -> 2 H2O + 2 Br2}$$ How do we approach finding the rate law of reaction? Can this be found out only through experiments?
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1answer
3k views

What to do when there is an odd number of valence electrons left on the the central atom?

For example, I'm trying to write the formula for $\ce{NO}$, and $\ce{ClO2}$. The steps my teacher gave me always assume that the central atom has a full valence, or more than full, after the outer ...
1
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1answer
115 views

How should I construct the orbitals of dilithium using only pen and paper?

For a week I have lessons about quantum chemistry and I have a trouble understanding how to arrive at the good answer for the drawing of the orbital $(\ce{III})$ for $\ce{Li2}$ (see the second picture)...
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2answers
2k views

Volume change inside a balloon upon decreasing the the outer pressure

A balloon is filled with hydrogen at room temperature. It will burst if pressure exceeds 0.2 bar. If at 1 bar pressure the gas occupies 2.27 L volume, upto what volume can the balloon be expanded? ...
0
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1answer
628 views

ph & pOH - Autoionization of Water

So I was learning about pH and pOH and it made sense. I looked at strong, weak acids & bases and learned that they dissociate completely in water. So then I moved on to water and learned about the ...
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2answers
630 views

Naming rules and acidity of Cl2CHCH2COOH

How do we name $\ce{Cl2CHCH2COOH}$ ? Is seeing branched chain our number 1 priority so we name it 1,1-dichloro-3-propanoic acid? also Which is more acidic $\ce{Cl2CHCOOH}$ or $\ce{Cl2CHCH2COOH}$ ?...
5
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2answers
379 views

Development of retrosynthesis plan

I need to retro-synthetically design a valid synthesis plan (in 2 steps, from cheap starting materials available over at Sigma Aldrich) for a target compound, pictured below. How would I go about ...
4
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2answers
3k views

Problems in the concept of ionic equilibrium

While trying to understand the solution of a problem given in my text book, I realized I'm having some difficulty with the solution. The problem is as folows: The ionization constant of HF is $3.2 \...
4
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1answer
785 views

Finding average half life of radioactive nuclide which undergoes two different decays

Find the average life of a radio nuclide which decays by parallel paths $$A\rightarrow B$$ $$2A\rightarrow B$$ where the decay constants are $\lambda_1=0.018\ \mathrm{s}^{-1}$ and $\lambda_2=0.001\ \...
4
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2answers
2k views

How do I find out what benzene containing compound this is with IR and NMR?

I have the following IR and NMR of an unknown substance. Can someone tell me what is a possible structure of the compound or point me in the correct direction. So far I am thinking of a benzene ring ...
4
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1answer
5k views

Constitutional isomers of cis-1,2-dibromocyclopentane

The following is a problem from Fundamentals of Organic Chemistry by McMurry. Draw two constitutional isomers of cis-1,2-dibromocyclopentane. I don't get how there can be constitutional isomers for ...
4
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1answer
427 views

Dissolving limestone in HCl and then neutralising the solution with NaOH

$15.0~\mathrm{mL}$ of $1.4~\mathrm{M}\ \ce{HCl}$ was mixed with $1.00~\mathrm{g}$ of limestone (impure $\ce{CaCO3}$) until all the solid had dissolved. The solution was then transferred to a conical ...
4
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1answer
2k views

Do ALL conversion factors have an infinite number of sigfigs?

Conversion factors have an infinite number of sigfigs, right? They should be exact values; but not all of them are, are they? I looked at http://www.webassign.net/question_assets/buelemphys1/...
4
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1answer
10k views

Lewis structure of diazomethane

I tried to google and watch youtube videos on how to do lewis structures properly, but I cant seem to understand how to do this properly. My teacher, when class was in session, gave me a set of ...
3
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1answer
821 views

How Many mL of 1.0M HCl Would be Required to Completely Decompose Sucrose into Glucose and Fructose?

I am currently conducting an experiment into the glucose content of certain sports drinks. However, I have hit a roadblock. A majority of the drinks that I intend to test contain sucrose. I am ...
3
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2answers
463 views

How can 2-indanone be prepared?

How do I prepare 2-indanone? Would adding phosgene to ortho-xylene lead to the formation of 2-indanone?
3
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1answer
2k views

Amine inversion and effect on basicity

What is amine inversion, and how does it affect basicity? For instance, why is $\ce{Et3N}$ less basic than (2.2.2.)cyclohexyl-amine despite the $+I$ from ethyl groups? The answer here is (c).
3
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1answer
6k views

Draw a simplified MO diagram for the pi system of Methyl vinyl ether

My attempt at the answers: i) 2 bond pairs and 2 lone pairs on oxygen atom therefore bond angle of slightly less than 109.5 degrees, around 104 degrees. ii) 120 degrees bond angle therefore sp2 ...
3
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2answers
942 views

Are the bonds within bismuth pentafluoride (BiF5) covalent or ionic?

When googling $\ce{BiF5}$ most results call it bismuth pentafluoride such as Wikipedia. I was under the impression that, since it is an ionic-bonded compound, Roman numerals should be used to ...
3
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2answers
3k views

Boron trihalides acidity

Boron trihalides ($\ce {BX3}$) is a Lewis acid, because it can accept an electron pair, as Gilbert N. Lewis definition. Now my question is, please arrange ($\ce {BF3}$), ($\ce {BCl3}$), ($\ce {BBr3}$),...
3
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1answer
353 views

Acidity In Organic Compounds

Why is the acidity order true? \[\ce{CH3COCH3 > CH3CO2CH3 > CH3CON(CH3)2}\] I deduced that in second and third option there is a $-I$ effect of the methoxy group, $\ce{N(CH3)2}$ and a $+R$ effect, ...
3
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1answer
4k views

Balancing the redox disproportionation of chlorine by half-reactions

I am having some difficulty balancing the following reaction using the half-reaction method: $$\ce{Cl2(g) -> Cl^{-}(aq) + ClO3^{-}(aq)}$$ My attempt at the problem: By determining oxidation ...
3
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1answer
335 views

Amphoteric amino acid titration

Glycine $(\ce{NH2CH2COOH})$ is an amino acid with two $\mathrm{p}K_a$ values $(\mathrm{p}K_{a,1}=2.0, \ \ce{COOH};\ \mathrm{p}K_{a,2}=10.0, \ \ce{NH2})$. (a) If $0.01~\mathrm{mol}$ of this amino ...
2
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1answer
630 views

Why can't electrons be transferred using hydrogen ions?

I have a homework question that asks: Recognizing how oxidation and reduction occurs is essential for analyzing and understanding biochemical reactions. Which of the following methods would NOT be ...
2
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0answers
575 views

Precipitation of citric acid by CaCl2 and Ca(OH)2? [closed]

I need to precipitate citric acid from an aqueous solution in the form of calcium citrate. There are, to my knowledge, two different methods of doing this: using $\ce{CaCl2}$ and which will react ...
2
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1answer
5k views

Solubility of calcium hydroxide determined by titration

For a lab I had to determine the solubility and $K_{sp}$ of $\ce{Ca(OH)2}$ by performing two different titrations. I am given the formula to find solubility in molarity it is as written below. ...
2
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1answer
246 views

Kinetics of an irreversible bimolecular reaction

Assume the reaction $$\ce{A + B ->} \text{Products}$$ is of second order kinetics and that the rate constant is $k$. The differential equation is given by $$\frac{\mathrm d}{\mathrm dt} [\ce{A}...
2
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1answer
16k views

Calculating pH: Weak Acid, Strong Base

This is a question that had me puzzled for quite a while. I feel that information is missing. A weak acid, $\ce{HA}$, $K_a = 1.0$ x $10^{-4}$, is titrated with $\ce{NaOH}$. At the equivalence point,...
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4answers
6k views

How to find the empirical formula for an nitrogen oxygen compound from the given mass of nitrogen and the product?

$5.00~\mathrm{g}$ of nitrogen is completely converted into an oxide of nitrogen. The mass of the oxide formed is $19.3~\mathrm{g}$. The empirical formula of the oxide would be? My working: $$\ce{...
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2answers
2k views

Why are more electronegative atoms better leaving groups?

My book says, "halide anions are electronegative and can easily stabilise negative charge, hence are good leaving groups." 1) what exactly does "stabilising negative charge" mean? I have read: " ...