Questions tagged [homework]
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175
questions
-1
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2answers
56 views
Intesive Properties - Temperature [closed]
Why is the temperature of a sample of matter intensive?
I don't think it would be extensive, but I also don't see why it would be intensive, either.
It's a very basic and easy question, but I can't ...
0
votes
1answer
5k views
Unit conversion of Molar Conductivity
I know this might be a silly question but I am confused with different answers of internet. My question is:
Molar conductivity is given as:
Molar conductivity = $\frac{\kappa}{M}$.
S.I. unit of :
$...
0
votes
2answers
2k views
Temperature Dependent Specific Heat of Nitrogen
Calculate the change in enthalpy as 1kg of nitrogen is heated from 1000K to 1500K, assuming the nitrogen is an ideal gas at a constant pressure. The tempreature dependent specific heat of nitrogen is ...
0
votes
1answer
854 views
Effect of an inert gas on steam vapor pressure at equilibrium
Suppose we have a closed container with mobile walls, so it will change its volume in order to equal the external pressure(constant) to the internal pressure.
This container has inside it a liquid ...
0
votes
1answer
1k views
How do I calculate the enthalpy change when a gas is being used to heat water?
The question I'm trying to answer is:
Calculate the mass of butane gas that would be needed to heat $724\ \mathrm{cm^3}$ of water from an initial temperature of $7.44\ \mathrm{^\circ C}$ to $50.7\ \...
0
votes
2answers
117 views
Hydrolysis of Radiolabeled Esters
Hydrolysis of C$_6$H$_5$COO$^{18}$CH$_3$ with aqueous NaOH produces what final product.
(a) CH$_3$$^{18}$OH
(b) CH$_3$CO$^{18}$ONa
(c) CH$_3$C$^{18}$OONa
(d) CH$_3$$^{18}$ONa
(e) CH$_3$OH
The ...
0
votes
2answers
5k views
How to calculate the molar mass of a protein from its osmotic pressure?
I am unsure how to go about solving this question. I know how to get the osmotic pressure, but where do I go from there?
I can't use the gas law since the protein is not a gas.
$\pu{2.38 g}$ of a ...
0
votes
1answer
39k views
Metal vs. Styrofoam cup calorimeter?
For a metal cup as opposed to a styrofoam cup calorimeter, do you expect the enthalpy of the reaction to be higher, lower, or the same?
I think the enthalpy of the reaction would be the same in the ...
0
votes
1answer
4k views
Galvanic cell using NaCl, Cu and Zn, why does it work?
Got a paper due tomorrow in chemistry, and my friends and I are totally stuck on this:
Basically we mixed some regular salt (NaCl) into a glass of water and stuck a zinc nail and a copper nail into ...
0
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1answer
2k views
Relation between number of equivalents of reactants
Consider the reaction $\ce{Sb2S3 + F2 -> SbF5 + SF6}$. If the milliequivalents of antimony, sulfur and fluorine are x, y and z respectively, then prove that $x+y=z$.
This is what I know: Number of ...
0
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2answers
380 views
What type of reactions are used in this synthesis?
The compound $\ce{(CH3)2CHCH2NH2}$ can be synthesised by the following route.
$$\ce{CH3CH=CH2 ->[1] CH3CHBrCH3 ->[2] (CH3)2CHCN ->[3] (CH3)2CHCH2NH2}$$
What types of reaction are used in ...
0
votes
2answers
7k views
How does this method of calculating the water equivalent of a calorimeter work?
I am doing a AP Chemistry lab in which we determine the heat capacity of a calorimeter (a concept that seems like it should depend on a lot more than just the calorimeter.) We have to calorimeters ...
0
votes
1answer
4k views
How to make copper plating solution?
I intend to make the following composition of copper plating solution:
\begin{array}{c:c}
\rm material & \rm concentration \\\hline
\rm Copper sulfate & \pu{200 \frac{g}{L}} \\
\rm ...
0
votes
2answers
21k views
How does the polarity of the eluent and sample affect the Rf value in thin layer chromatography?
A three-component mixture (X, Y, Z) was separated using normal phase TLC. Three eluents of varying polarity were used. Select the TLC plate that was developed using the least polar eluent (click on ...
2
votes
0answers
763 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 ...
0
votes
1answer
2k views
Osmotic pressure of a solution of a protein?
A small protein molecule, code-named "sloth", has a MM of $\mathrm{1.50 x 10^4}$ g/mol. What is the osmotic pressure exerted at $\mathrm{24.0^oC}$ by 25.0 mL of an aqueous solution that contains $\...
1
vote
0answers
317 views
Does PO3- exist as a free ion or in a cyclic/linear polymeric form? [closed]
My book says that $\ce{PO3-}$ exists as cyclic or linear polymeric structure but doesn't elaborate on this. I Googled this and found no result either.
Also, what would be the structure of $\ce{PO3-}$...
0
votes
1answer
758 views
Simple Distillation of Unknowns
Can an identification experiment (using acetonitrile, isopropyl, and cyclohexane) using simple distillation and boiling point be improved by using a digital thermometer?
Can simple distillation be ...
0
votes
2answers
145 views
What is the wavelength of an electron?
The kinetic energy of an electron is $1.67 \times 10^{-17}\mathrm{J}$. Calculate the wavelength ($\lambda$) of the electron.
I know the formula $\lambda= \frac{h}{mv}$; where h is Planck's constant.
...
0
votes
1answer
893 views
Explain the difference in stability of permanganate ions in acidic/ alkaline solutions?
The question is such:
Use the data to comment on the stability of $\ce{MnO4-}$ in acidic and basic solution. Suggest a reason for this difference.
$$\begin{align}
&\text{acidic solution:}&...
-1
votes
1answer
1k views
Finding the molarity of an acid in a titration
I was doing a question that asks the molarity of a 10 mL of tartaric acid that is titrated to phenolphthalein endpoint with 20 mL of 1.0 M NaOH.
I worked it out by equating the molarity of the NaOH ...
0
votes
1answer
5k views
How to round correctly when calculating the average and standard deviation?
Is my Chemistry book wrong on the significant figures in this exercise?
Why did they round to 0.16 instead of 0.1580 ?
Also why did they round down the means?
0
votes
2answers
24k views
How to write equations for dissociation of ionic compounds in water?
Please write a dissociation-in-water equation for the compounds $\ce{BeI2}$ and $\ce{LiI}$. Make sure to add the states of matter after each compound.
Currently, for $\ce{BeI2}$ I have the equation $$...
0
votes
1answer
2k views
How to determine the percentage of iron(II) and iron(III) in a solution?
Outline a plan of an experiment to determine the percentage of iron
present as iron(III) in a solution containing $\ce{Fe^3+(aq)}$ and $\ce{Fe^2+(aq)}$
ions. You are provided with zinc, a standard ...
0
votes
2answers
45k views
How to determine which aqueous solution has the largest freezing point depression
Question
This is more of a conceptual question. Let's say that we are given different aqueous solutions and we are asked to choose the one with the highest freezing point depression, which do we ...
0
votes
2answers
4k views
What happens to acids/bases left out overnight?
I conducted a titration experiment a few days back and was unable to neutralize the solution in time, so I had to leave the solutions of HCl and NaOH out overnight in order to use them the next day. ...
0
votes
1answer
1k views
How high in (mmH2O) is the column of water in the tube?
A long glass tube, sealed at one end, has an inner diameter of 23.4 mm. The tube is filled with water and inverted into a pail of water. If the atmospheric pressure is 735 mmHg, how high (in mmH2O) is ...
0
votes
2answers
4k views
Calculating molar conductance of CaCl2
Ok, so the following question is given in my text book.
Of the molar conductance value of $\ce{Ca^2+}$ and $\ce{Cl^-}$ at infinite dilution are respectively $118.88\times10^{-4}$ and $77.33\...
0
votes
2answers
9k views
Why and how carboxylate ion has greater stability than carboxylic acid?
I found it written in my textbook. I think it's a misprint, I can't think of any logic behind this statement.
I've only learned that ion is less stable specie so carboxylate ion cannot be more stable ...
0
votes
1answer
124 views
Arranging different oxygen-containing organic compounds by decreasing acidity
I am facing difficulty in the following problem.
Arrange the following compound in decreasing order of acidity.
It is clear that conjugate base of (Q) is more stable.hence it is most acidic.in R) ...
0
votes
2answers
1k views
When finding hybridisation of atoms, why are double bonds and triple bonds only considered once?
To figure out what hybridization an atom has is to just count the number of atoms bonded to it and the number of lone pairs. Double and triple bonds still count as being only bonded to one atom. (...
0
votes
1answer
324 views
Equivalent Line Angle Structures?
Are the following equivalent structures for 2,2-dimethylpropane?
I think so, because my rendering simply rotates the cross 45 degrees!
Also, regarding 3,3-diethylpentane, are these both equally ...
0
votes
1answer
301 views
Using gas laws to find density
An unknown gas at $\mathrm{63.1\ ^\circ C}$ and $\mathrm{1.05\ atm}$ has a molar mass of $\mathrm{16.04\ g/mol}$.
What is the density of the gas?
I know I need to use the $pV=nRT$ equation but it ...
0
votes
2answers
1k views
How can I derive whether the methyl cation or anion is planar?
According to VSEPR theory, in which species do all the
atoms lie in the same plane?
$\ce{CH3+}$
$\ce{CH3-}$
(A) 1 only (B) 2 only (C) both 1 and 2 (D) neither 1 nor 2
My try:
...
0
votes
1answer
2k views
Reaction of 1,1-diphenylethanol on Montmorillonite K10 under microwave radiation
What is the product of 1,1-diphenylethanol + Montmorillonite K10 Clay undergoing microwave radiation? What is the mechanism for it?
My effort:
1,1-diphenylethanol + Montmorillonite K10 Clay catalyst ...
Klaus-Dieter Warzecha
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0
votes
1answer
56 views
Mr of Acid getting wrong answer
I am preparing for A level chemistry exams. One of the questions I came across is
Calculate the $M_\mathrm r$ of unknown monoprotic acid. The volume is $15\,\rm cm^3$ and concentration $10.95\,\rm ...
Klaus-Dieter Warzecha
42.8k8 gold badges95 silver badges159 bronze badges
0
votes
1answer
160 views
Fe/Ga cell has a negative potential?
In the following homework problem, the answer says:
"$E ^{o}_{cell}$ is negative, which makes the $\ce{Fe}$ and $\ce{Ga}$ half-reactions non-spontaneous."
But I found $E ^{o}_{cell}$ to be positive ...
0
votes
1answer
301 views
Is 2,3-dimethylprop-1-ene a possible organic structure?
Is 2,3-dimethylprop-1-ene a possible organic structure?
I am not sure how to approach this, what would the correct name of this molecule be?
0
votes
1answer
2k views
When an expansion of a system does work on its surroundings, is the sign for work negative?
This question comes to me from trying to explain the answer $1.67\ \mathrm{L}$ of this question:
A cylinder with a moving piston expands from an initial volume of $0.250\ \mathrm{L}$ against an ...
0
votes
3answers
6k views
Basicity of substituted pyridines
Which of the following pyridines are most basic?
I would've considered D, since chlorine is the most electronegative, and would therefore have the largest partial negative charge, making it more ...
0
votes
2answers
118 views
If PQ, T2U2, RS2 and VW4 have the same Ksp, which has the lowest solubility in moles of solute per litre?
If the solubility products of the following ionic compounds all have the same numerical value, and all solubilities have values between zero and one, which one would have the lowest solubility in ...
0
votes
1answer
55 views
Why assume a neutral amino acid is given for acid-base reaction?
The questions is:
$1.812\ \mathrm{g}$ of a crystallized α-amino acid ($\mathrm{p}K_\mathrm{a1} = 2.4, \mathrm{p}K_\mathrm{a2} = 9.7$) has a $\mathrm{pH}$ of $10.4$ when dissolved in
$100\ \mathrm{...
0
votes
1answer
1k views
Hess's Law/Enthalpy of reaction
The problem:
Chloroform, $\ce{CHCl3}$, is formed from methane and chlorine in the
following reaction:
$$\ce{CH4(g) + 3Cl2(g) ->3HCl(g) + CHCl3(g)}$$
Calculate $\Delta rH^{\circ}$, ...
0
votes
1answer
333 views
Interpretation of an H NMR
I am fairly new to NMR and require assistance to analyze and interpret the NMR I have provided (sorry for it being vertical). This is an unknown compound that I have derived during one of my lab ...
0
votes
1answer
8k views
Calculating collision diameter with viscosity, but not having the mass given
I've got a homework question i'm stumped on.
The viscosity of the ethylene gas was measured at $99.8\times10^{-7}\ \mathrm{N\ s\ m^{-2}}$ at $288\ \mathrm K$. Calculate the collision diameter in $\...
0
votes
1answer
5k views
How to calculate the pH of a propanoate buffer after addition of sodium hydroxide?
I've calculated the pH of the buffer solution, as seen.
The question I'm referring to is part d), which asks: 'Calculate the pH of the solution after 0.01 mols of NaOH are added to 500$cm^3$ of the ...
Klaus-Dieter Warzecha
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0
votes
2answers
3k 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?
...
Klaus-Dieter Warzecha
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0
votes
1answer
4k views
How to calculate concentrations in a diluted mixture of multiple solutions?
I have a homework problem as follows:
A solution was prepared by mixing $25.0\ \mathrm{mL}$ of $0.208\ \mathrm{M}$ $\ce{Fe(NO3)3}$ and $4.50\ \mathrm{mL}$ of $0.00190\ \mathrm{M}$ $\ce{KSCN}$ and ...
0
votes
2answers
2k views
Determining boiling point on a created temperature scale
1.Assume that you construct a thermometer using gallium as the fluid instead of mercury, and that you define the melting point of gallium as 0 °G and the boiling point of gallium as 1000 °G. What is ...
0
votes
2answers
3k views
Reaction of solid metals with a solution of metal ions
Explain the following experiments and their results. What is their chemical equations as well?
When immersing a Magnesium (Mg) chunk inside aqueous solution of Copper ions (Cu(II)), a red-brown ...