If your question is part of your high school or college/university homework, please use this tag. It signifies that instead of a direct answer, care should be taken to explaining the steps to the solution, preferably sticking to just giving helpful, conceptual hints. This tag may be applied to ...

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states of matter [on hold]

a vertical hollow cylinder of height 152 cm is fitted with the weightless piston. the lower half is filled with an ideal and upper half with mercury. the cylinder is now heated at 300K so that 1/4th ...
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1answer
44 views

What do the half-reactions need to be for balancing a redox reaction in an acidic medium?

Question: Balance the following reaction: $\ce{CuS + SO4^{2-} -> CuO + SO2}$ My Efforts: Number mentioned in the brackets oxidation number of S I have found out that the oxidation ...
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4answers
83 views

What is the proper Lewis structure for HCOOH?

I tried to draw the Lewis structure of $\ce{HCOOH}$ but I didn't get the correct representation. As you can see in the picture below, at no. 1, I put $\ce{C}$ as the central atom because it has less ...
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Help me wrap my head around thermodynamics

Calculate the final temperature and the change in internal energy when $500\:\mathrm{J}$ of energy is transferred as heat to $0.900\:\mathrm{mol}$ $\ce{O2(g)}$ at $298\:\mathrm{K}$ and ...
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1answer
33 views

How to calculate the yield of hydrogen obtained by zinc reduction from hydrochloric acid? [on hold]

Hydrogen gas is produced when zinc reacts with hydrochloric acid. If the actual yield of this reaction is $85\%$, how many grams of zinc are needed to produce $112~\mathrm{L}$ of $\ce{H2}$ at STP? ...
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28 views

Is Oxygen a Lewis acid?

As I recall a Lewis acid is a substance that can accept an electron pair from a donor substance and oxygen seems to be able to do that for example in $\ce{H2 + O -> H2O}$ so is oxygen a Lewis ...
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17 views

Came across an interesting question on titrations

What amount of substance containing 60% NaCl, 37% KCl should be weighed out for analysis so that after the action of 25 ml of 0.1 N AgNO 3 solution, excess of Ag+ is back titrated with 5 ml of NH ...
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1answer
12 views

Calculating the molar mass of a solute from freezing point

A 4.305-g sample of a nonelectrolyte is dissolved in 105 g of water. The solution freezes at -1.23C. Calculate the molar mass of the solute. Kf for water = 1.86C/m. My steps: 1.23=1.86 * x/1.05 ...
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1answer
73 views

Finding the Oxidation number

I have got the homework to balance the following redox reaction. $\ce{Cr(OH)3- + HO2- -> Cr2O7^{-2} + OH- }$(Basic medium) To balance this reaction first thing we need to do is to find the ...
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1answer
74 views

Can two positive ions be next to each other in a formula?

Lets say I want to find the oxidation numbers of a formula. For example: $\ce{H3AsO3}$ Oxygen has a 2- charge. They're 3 of them, so its 6- Hydrogen has a 1+ charge. They're 3 of them, so its 3+. ...
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21 views

Equation Stoichiometry & Gas Law Question [closed]

I have been trying to solve this problem, i've done it several ways, and yet it stil isn't the right answer. Please help!
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1answer
41 views

When are we justified in making assumptions in questions

The density at $20^\circ\mathrm{C}$ of a $0.500~\mathrm{M}$ solution of acetic acid in water is $1.0042~\mathrm{g/mL}$. What is the molality of the solution? The molar mass of acetic acid is ...
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1answer
92 views

Is there an easy way to remember charges on ions?

I have a chemistry test coming up and I might need to know the charge that goes with the different ions like $\ce{SO4}$ has $-2$, $\ce{NO2}$ is $-1$ and $\ce{PO4}$ is $-3$. Is there an easy way to ...
2
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1answer
29 views

Why is oxygen absorbed in a colorless alkaline solution of pyrogallol and why does it turn dark brown?

I'm reading about recognition and identification of gases. My book says: Oxygen is absorbed in colorless alkaline solution of pyrogallol and turns dark brown? I'd like to know why and how. ...
2
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1answer
42 views

Wavelength of X-rays

What will be the wavelength of X-ray if we apply a potential difference of , say 20 KV across the ends of the x-ray tube ? Alright, i started with the modified de-broglie equation ...
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1answer
40 views

What is the difference between a bond, force, and interaction?

I am trying to explain why some solids are more soluble in water than others: So the energy released from the formation of bonds between the solid solute molecules and water molecules compensate the ...
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0answers
43 views

Determine the ΔH for the reaction in kJ/mol of ethanol?

A $1.000~\mathrm{g}$ sample of ethanol, $\ce{C2H5OH}$, was burned in a bomb calorimeter whose heat capacity had been determined to be $2.71~\mathrm{kJ/C}$. The temperature of $3.000~\mathrm{kg}$ of ...
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0answers
33 views

Neutralisation of HCl with NaOH - generated heat and excess concentration [closed]

If you have $75\:\mathrm{mL}$ of $M(\ce{HCl}) = 4\:\mathrm{M}$ at $25\:\mathrm{^\circ C}$ and $100\:\mathrm{mL}$ of $M(\ce{NaOH})=5\:\mathrm{M}$ at $27\:\mathrm{^\circ C}$ with a final temperature ...
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2answers
24 views

Calculate the second ionization energy for the Mg from the following data?

here is a problem : What I did " as shown in the picture below " I rewrote the information given in terms of reactants and products ( equations )// in Part 1 Then I used the Hess law to obtain ...
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1answer
25 views

Thermodynamic question - Work during a reversible compression

I have a short multiple choice question that I have already solved. The question is The work done during a reversible compression (Vi (initial) = V1; Vf = 1/6V1) of an ideal gas is? I chose ...
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1answer
38 views

Determining covalent bond strengths without hybridisation

Assuming pure $\ce{2s}$ and $\ce{2p}$ orbitals of carbon are used in forming $\ce{CH4}$ molecule, which of the following statements is false? (single choice question) Three $\ce{C-H}$ bonds ...
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1answer
17 views

Calculate the Molarity of a soln

Having ethanol with its mole fraction equal to $0.040$, assume the density of water to be 1. I used this method, is it correct? Moles of $\ce{H2O} =0.96$ Therefore mass is equal to $0.96\cdot18 ...
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3answers
196 views

How can metals like magnesium and sodium burn underwater?

I can't find the answer anywhere else and I need it for an essay (I'm in 8th grade). Please answer with as much detail as possible (though any help is appreciated). Any websites I have found have ...
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1answer
41 views

Moles to Moles question for my online homework

Online homework problem: How many moles of water vapor react to yield 151.52 moles of hydrogen? I did, $$x \text{ mol } \ce{H2O} = 151.52 \text{ mol }\ce{H2} \frac{1 \text{ mol } \ce{H2O}}{3 ...
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25 views

Supercritical Steam Expansion

Ten $\mathrm{kg}$ of steam at $500~\mathrm{bar}$ is expanded at constant pressure until its volume increases to seven times its initial value of $0.01~\mathrm{m^3}$. (a) Calculate the initial and ...
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1answer
33 views

Differentiating between Titration, Buffer, diluted buffer, Deionized H₂O

I had a chemistry lab where we had to titrate three solutions with HCl, a buffer, a diluted buffer and deionized water. My partner and I didn't label the charts we made, so now I have to figure out ...
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3answers
59 views

Why is CaCl2 called Calcium chloride?

Doing a first year chem class. Just read through the molecular naming of compounds and now I'm confused as to why CaCl2 is called calcium chloride and not calcium dichloride?
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1answer
39 views

…If the final temperature of the combined liquids is 28.5 C and heat capacity of the calorimeter is 19.3J/C determine the specific heat of methanol?

A question in the book says : A $25.95 g$ sample of methanol at $35.6 °C$ is added to a $38.65 g$ sample of ethanol at $24.7 °C$ in a constant pressure calorimeter If the final temperature pf the ...
3
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1answer
115 views

Kinetics of Interstellar Chemistry — Applying steady state to formation of H₂

I am trying to solve problem 2 from the 2009 International Chemistry Olympiad (IChO), which is as follows: If two atoms collide in interstellar space the energy of the resulting molecule is so ...
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1answer
30 views

What total energy (in kJ) is contained in 1.0 mol of photons, all with a frequency of 2.75 • 10¹⁴ Hz?

There is a question, that says: What total energy (in $\mathrm{kJ}$) is contained in $1.0~\mathrm{mol}$ of photons, all with a frequency of $2.75 \cdot 10^{14}~\mathrm{Hz}$? My answer was: The ...
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2answers
128 views

Help with identifying an unknown substance?

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 ...
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3answers
158 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 ...
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1answer
35 views

How do I find a concentration from a sample tested on a spectrophotometer?

I have an assignment to calculate the concentration from a sample. The assignment is: You have 100 µL of RNA. You take 10 µL from the sample and put it in 990 µL of water in the cuvette. The OD is ...
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47 views

I need help with this exercise i need to find all chem elements

White solid A water insoluble cleaved hot to solid gas B and C. B is insoluble in water and in $\ce{HCl}$ but soluble to $\ce{HNO3}$ the react gives solution D and E colorless gas which becomes red ...
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1answer
44 views

Is this Hess's Law Electrochemistry question incorrect?

It is my understanding that to apply Hess' Law to this equation the top equation sign would be reversed and the outcome would be +0.65 V. Often the system produces incorrect answers. I was looking ...
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1answer
46 views

Figuring out the pH

So, I'm refreshing my college chemistry a bit. Could someone give me a pointer on the following practice exercise? What is the pH @ 25 degrees Celcius in a bucket with 10liter pure water in which a ...
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1answer
36 views

Relationship between Van der Waals forces and the boiling point

Choose the right answers in the following statement: The boiling point of a liquid substance is higher as the Van der Waals forces (in/between) the molecules of the substance are (lower/higher). I ...
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1answer
32 views

Carbonate Equilibrium Question: Finding concentration using concentration ratio and number of moles of acid

Lake water contains dissolved sodium carbonate and sodium hydrogen carbonate. The following equilibrium exists: $\ce{HCO3- <=> H+ + CO3^{2-}}$ $\frac{\ce{[CO3^{2-}]}}{\ce{[HCO3-]}} = 0.958$ ...
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2answers
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Adding concentrations to obtain mass

I have a question that gives two concentrations and asks for the mass of HCl formed by the reaction. I have two concentrations: 250mL of 4.00M $\ce{H2SO4}$, and 250mL of 1.00M $\ce{NaCl}$. Here is ...
3
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1answer
65 views

Can Lead (Pb) oxidize Tin (Sn)?

According to my textbook, element $\ce{X}$ can oxidize element $\ce{Y}$ if $\ce{X}$ was lower in the activity series. Lead is lower than Tin in the activity series table in the textbook, but the ...
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1answer
29 views

Thermodynamics Problem

If we put a piece of coal in open air we don't get any energy of it.But if we put fire to it in open air we get energy.Explain it with help of Gibbs free energy.
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29 views

titration of tungsten and HCl with KMnO4 as indicator

Find out the percent wo in the ceramic sample Tungsten trioxide ($\ce{WO3}$) has a rich yellow color and is often used as a pigment in ceramics and paints. In order to test a ceramic vase for its ...
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1answer
30 views

How many moles of GeF4 are needed to produce 8.00 mol of GeF3H?

GeF3H is formed from GeH4 and GeF4 in the combination reaction: GeH4 + 3GeF4 → 4GeF3H If the reaction yield is 92.6%, how many moles of GeF4 are needed to produce 8.00 mol of GeF3H? I know that ...
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1answer
28 views

Calculating Electronegativity of Fluorine [closed]

Calculate the electronegativity of Fluorine from the following data. EH-H = 104.2 kcal/mol EF-F = 36.6 kcal/mol EH-F = 134.6 kcal/mol XH = 2.1 How to solve? Any wiki or link to somewhere where ...
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1answer
55 views

Molecular Formula Problem

Hydralazine is a drug used to treat heart disease. It is 59.99% carbon, 5.03% hydrogen, and 34.98% nitrogen and has a molecular mass of 160.178. What is the molecular formula for hydralazine? I did, ...
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1answer
37 views

Which is more acidic? CO or CO2?

Q1)Which of the given compounds is most acidic? $\ce{CO}$ or $\ce{CO2}$ ? How to solve(explanation)? EDIT: Q2) $\ce{BeO}$ is amphoteric while $\ce{B2O3}$ is acidic - True/False?
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2answers
66 views

Ionization Energies of Sulphur and Oxygen Anions

Which of the following are in the correct order of their Ionization Energies?(Multi-Answer Question) a) $\ce{O > S > S- >O-}$ b) $\ce{F > F- > Cl- > Cl}$ c) $\ce{O > O- ...
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2answers
38 views

Finding the initial concentration

The solubility product of $\ce{AgBr}$ is $7.7 \cdot 10^{-13}\:\mathrm{mol^2/L^2}$. What was the initial concentration of $\ce{AgNO3}$ solution, if the precipitation of $\ce{AgBr}$ appears after the ...
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1answer
42 views

what is the formula of potassium ammonium sulfate?

I tried to get the formula of potassium ammonium sulfate what I got is $\ce{K(NH4)2SO4}$ but I don't think this the right formula I searched in google, I found an answer : $\ce{KNH4SO4}$ BUT I don't ...
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2answers
48 views

Sulphur oxoacid forming

I got this reaction and I can't figure out the end products $$\ce{SO2 + S + CaO + Na2SO4 -> Na2S2O3 + ~?}$$ Guessing some calcium sulphur salt should form, but which one?