Questions tagged [homework]
DEPRECATED. DON'T USE THIS TAG.
173
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Does no optical rotation always implies optical inactivity? [duplicate]
This question popped up in my mind in reference to this question,
Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles?
Suppose that I give a chemistry ...
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2
answers
79
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Inhibitors reaction at home
For a school science project, my teacher asked me to find a reaction that can be slowed down with an inhibitor and film it at home/lab at school. He told not to use lemon on an apple or anything ...
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2
answers
69
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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 ...
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2
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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 ...
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1
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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 $\...
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846
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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 ...
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1
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6k
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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 :
$...
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2
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6k
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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. ...
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2
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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 ...
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141
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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) ...
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2
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2k
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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. (...
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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 ...
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2
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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:
...
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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 ...
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239
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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 ...
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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 ...
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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 ...
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3
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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 ...
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1
answer
6k
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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 ...
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240
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Attack at ketone vs carboxylic acid carbonyls
Why in this the nonbonding electrons of N group does not attack C2 as I think it is more electropositive ?
Then how pyruvic acid is converted to alanine.
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How would you go about solving this pH problem?
What is the $\mathrm{pH}$ of a $0.24\ \mathrm M$ solution of benzylammonium chloride ($\ce{C6H5CH2NH3Cl}$)?
$K_\mathrm b$ for benzylamine is $2.2\times10^{-5}$
Your answer must be within $\pm 0.4\ ...
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How do I arrive at the mass of solvent from a molar fraction concentration?
So the question says:
If the mole fraction for $\ce{H2SO4}$ in an aqueous solution is $0.325$, what is the mass of water (in grams) in $100\ \mathrm{mL}$ of solution?
Me, and my other classmates ...
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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 ...
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1
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3k
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Predicting the solution with the highest boiling point
I am facing problem with the following question:
Predict which solution will have the highest boiling point in increasing order?
$1~\%$ solution of $\ce{C6H12O6}$
$1~\%$ solution of $\ce{NaCl}$
$1~...
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412
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working with ratios and RMS to find variables
question
consider separate 1.0L samples of helium and $UF_6$ both at 1.00atm and containing the same number of moles. what will the ratio of the separate temperature need to be in order to have the ...
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How to find the rate of effusion given rates?
Question
At $25~^\circ\mathrm{C}$, a sample of $\ce{NH}$ effuses at the rate of $0.050$ moles per minute. Under the same conditions, what is the molar mass of a gas that effuses at approximately one ...
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The mass of a carbon-12 atom is 12 amu. What percent of the mass is located in the nucleus?
The mass of a carbon-12 atom is 12 amu. What percent of the mass is located in the nucleus? and Why is the value so close to 100%?
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Amount of Cl- needed to precipitate AgCl given Ksp and [Ag+]
Why is $0.25 \ \mathrm{mL}$ the correct answer in this problem?
I used the Ksp to find the molarity of Chlorine to be $3.47 \times 10^{-2} \ \mathrm{M}$.
Then I used the formula
$$\text{Molarity}_{...
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2
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539
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What type of reactions are used in this synthesis?
The compound $\ce{(CH3)2CHCH2NH2}$ can be synthesised by the following route.
$$\ce{CH3CH=CH2 ->[1] CH3CHBrCH3 ->[2] (CH3)2CHCN ->[3] (CH3)2CHCH2NH2}$$
What types of reaction are used in ...
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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?
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1
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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 ...
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855
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How to make by dilution a certain ion concentration
The question I'm trying to answer is this:
What volume of $0.25\ \mathrm{mol/l}$ calcium nitrate is required to make by dilution with water $500\ \mathrm{cm^3}$ of a solution with a nitrate ion ...
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1
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5k
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How do we count charges in this example of a Redox reaction equation?
My brother(younger) had a doubt regarding this chemistry book example so I let him here :
Question :
Balance the equation : $\ce{H+ + MnO4- + Fe^2+ -> Fe^3+ + Mn^2+}$
Solution steps(as given by ...
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1
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387
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Determination of initial excited state via luminescence
A one electron species initially in the some excited state
($n_i$)
is irradiated with a light of wavelength 121 nm when
the electron is promoted to a further higher orbit ($n_f$).
In
...
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2
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91
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What are the order of the reaction under the following conditions?
The experimental rate of a reaction
$$\ce{A + 2B -> C + D}$$
$$\frac{\mathrm dx}{\mathrm dt} = K[\ce{A}][\ce{B}]^2$$
Calculate the order of the reaction when (i) $[\ce{A}]\gg[\ce{B}]$ (ii) $[\ce{B}...
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642
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Empirical formula, simplifying problems
Need some help with second part.....can't get it to be balanced and therefore can't find the formula and name! Thanks in advance!
What is the empirical formula of each of the following compounds?
a)...
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1
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1k
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Finding the mole fraction
At $25\ \mathrm{^\circ C}$ the vapor in equilibrium with a solution containing carbon disulfide and acetonitrile has a total pressure of $263\ \mathrm{torr}$ and is $85.5\ \mathrm{mol}\text{-}\%$ ...
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votes
1
answer
991
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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 ...
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1
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67
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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{...
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320
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Explain why alumina-containing zeolites possess chemically active surfaces
I think zeolites possess acid sites that are catalytically active in many hydrocarbon reactions. The pore system only allows molecules that are small enough to enter, hence it affects the selectivity ...
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1
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22k
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Calculate the pH of Na2CO3
Given information:
$K_\mathrm{a}(\ce{H2CO3}) = 4.3 \times 10^{-7}$,
$K_\mathrm{a}(\ce{HCO3-}) = 4.8 \times 10^{-11}$,
${{\ce{[Na2CO3]}=0.20\ \mathrm{M}}}$
This was a question in an exam and I'm ...
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1
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3k
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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 ...
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1
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2k
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Find molar concentration of sodium carbonate dissolved in water
The question is
A solution of $\ce{Na2CO3}$ is made by dissolving $5.3~\mathrm{g}$ of the powder in enough water to make $250~\mathrm{mL}$ of solution. Find the molar concentration.
I have done ...
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1
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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 $\Delta rH^{\circ}$, ...
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1
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791
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How does a lower pH change the alcohol concentration of wine?
I have been told it that when the pH of wine is lowered the alcohol concentration will decrease because of Le Chatelier's Principle. Which states; if a equilibrium is disturbed by changing the ...
0
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1
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3k
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How to calculate the new concentration of a solution after adding more solute and convert it to ppm?
My question is the following:
$2~\mathrm{g}$ table salt is added to $0.5~\mathrm{m^3}$ water whose salt concentration is $10~\mathrm{mg\,L^{-1}}$. Compute the salt concentration of the mixture in ...
0
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1
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479
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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 ...
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1
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985
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How to calculate the amount of substance of nitrogen that dissolves in water?
The Henry's law constant for the solubility of $\ce{N2}$ gas in water at $298~\mathrm{K}$ is $10^5~\mathrm{atm}$. The mole fraction of $\ce{N2}$ in air is $0.8$. The amount of substance of $\ce{N2}$ ...
0
votes
1
answer
2k
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Calculating temperature after adding heat to ice
If $53.2~\mathrm{kJ}$ of heat are added to $15.5~\mathrm{g}$ of ice at $-5^\circ\mathrm{C}$, what will be the resultant state of matter in which water is present and also calculate its final ...
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2
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3k
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Volume of one equivalent of a gas
How do we define an equivalent when we are not talking about any particular reaction? Like, we say that equivalent volume of Oxygen is 5.6L, so we have taken the n-factor to be 4, and in CO2 we take n-...
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