Difference between Internal Energy and Enthalpy

Q. The heat of combustion of carbon to $C{O}_2$ is $-393.5kJ/mol$. The heat released upon formation of $35.2g$ of $C{O}_2$ from carbon and oxygen gas is:

1. $-630kJ$
2. $-3.15kJ$
3. $-315kJ$
4. $+315kJ$

Q. Explain Why:
gamma/(gamma-1)=m×Cv

Q. One mole of an ideal gas for which $C_v=\left(\frac{3}{2}\right)R$ is heated reversibly at a constant pressure of 1 atm from ${25}^{o}C$ to ${100}^{o}C$. The $△H$ is:
Given: R = 1.987 cal

1. $3.775\text{cal}$
2. $37.256\text{cal}$
3. $3725.6\text{cal}$
4. $372.56\text{cal}$

Q.

Which of the reaction defines $\Delta H_f^0$ ?

1. 

2. 

3. 

4. 

Q.

What does negative $∆\mathrm{G}$ mean?

Q.

What is the amount of work done when $0.5$moles of methane, ${\mathrm{CH}}_4\left(\mathrm{g}\right)$, is subjected to combustion at $300\mathrm{K}$? (given, $\mathrm{R}=8.314\mathrm{J}{\mathrm{K}}^{-1}{\mathrm{mol}}^{-1}$)

Q.

What are the objectives of thermodynamics?

Q.

Four monobasic acids a, b, c, and d have the values as $–11.5,–7.5,–12.4$ and $–8.9\mathrm{kcal}{\mathrm{mol}}^{-1}$. when they are neutralized by a common base the acidic character or base of the order

Q.

$(\Delta H-\Delta U)$ for the formation of carbon monoxide ($CO$) from its elements at $298K$ is ( $R=8.314J{K}^{-1}mo{l}^{-1}$)

1. $-2477.57Jmo{l}^{-1}$

2. $2477.57Jmo{l}^{-1}$

3. $-1238.78Jmo{l}^{-1}$

4. $1238.78Jmo{l}^{-1}$

Q. One mole each of $Ca{C}_2,A{l}_4{C}_{3}andM{g}_2{C}_3$ react with $H_{2}O$ in separate open flasks at ${25}^{o}C.$ Numerical value of the work done by the system is in the order:
Given reactions:
$Ca{C}_2\left(s\right)+2H_{2}O\left(l\right)\to Ca\left(OH{)}_2\right(s)+C_2{H}_2(g)$
$A{l}_4{C}_3\left(s\right)+12H_{2}O\left(l\right)\to 4Al\left(OH{)}_3\right(s)+3C{H}_4(g)$
$M{g}_2{C}_3\left(s\right)+4H_{2}O\left(l\right)\to 2Mg\left(OH{)}_2\right(s)+C{H}_3-C\equiv CH(g)$

1. $Ca{C}_2<A{l}_4{C}_3<M{g}_2{C}_3$
2. $Ca{C}_2=M{g}_2{C}_3<A{l}_4{C}_3$
3. $Ca{C}_2<M{g}_2{C}_3<A{l}_4{C}_3$
4. $Ca{C}_2>A{l}_4{C}_3>M{g}_2{C}_3$

Q.

What are the values of $∆\mathrm{H}$ for endothermic and exothermic reactions?

Q.

When is the heat evolved or absorbed in certain chemical reactions?

Q. Given the following standard heat of reactions :
(i) heat of formation of water = $-68.3kcal$
(ii) heat of combustion of acetylene = $-310.6kcal$
(iii) heat of combustion of ethylene = $-337.2kcal$
Which of the following option(s) is / are correct for the hydrogenation of acetylene at constant volume $\left({27}^{\circ }C\right)$ ?

1. Change in enthalpy of hydrogenation of acetylene is $-41.7\text{kcal}$
2. Change in internal energy of hydrogenation of acetylene is $-41.7\text{kcal}$
3. Change in enthalpy of hydrogenation of acetylene is $-41.1\text{kcal}$
4. Change in internal energy of hydrogenation of acetylene is $-41.1\text{kcal}$

Q.

Why cant a process violate the second law of thermodynamics?

Q. The orbitals having lower energy in tetrahedral complexes according to CFT are ?

1. $d_{xy},d_{yz}{d}_{2z}$
2. $d_{xy}=d_{yz}=d{x}^2-y^2$
3. $d_{xy},d_{yz},d_{zx}$
4. $d{x}^2-y^2,d_z^2$

Q.

In a reaction + heat is written on the right-hand side, what type of reaction is it?

Q. For the combustion of 1 mole of a liquid benzene at ${25}^{o}C$, the enthalpy is given by:
$C_6{H}_6\left(l\right)+\frac{15}{2}{O}_2\left(g\right)\to 6C{O}_2\left(g\right)+3H_{2}O\left(l\right)$ $\Delta H=-780980$ cal
What would be the internal energy of the reaction?

1. $-580kcal$
2. $580kcal$
3. $780kcal$
4. $-780kcal$

Q. For the reaction
$H_2{F}_2\left(g\right)\to H_2\left(g\right)+F_2\left(g\right)$
$\Delta U=–59.6kJmo{l}^{-1}$ at ${27}^{\circ }C$.
The enthalpy change for the above reaction is
(–) $kJmo{l}^{–1}$ [nearest integer]

Given : $R=8.314J{K}^{-1}mo{l}^{-1}$.

Q. For which of the following $\Delta H$ is not equal to $\Delta U$

1. $2HI\left(g\right)\to H_2\left(g\right)+I_2\left(g\right)$
2. $2S{O}_2\left(g\right)+O_2\left(g\right)\to 2S{O}_3\left(g\right)$
3. $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)$
4. $2N{O}_2\left(g\right)+\to N_2{O}_4\left(g\right)$

Q.

A man whose mass is 75 kg walks up 10 steps, each 20 cm high, in 5 s. Find the power he develops. Take g = 10 ms^–2.

Q. The heat of combustion of sucrose $\left(C_{12}{H}_{22}{O}_{11}\right)$ is $-5.65\times {10}^{3}kJ$. If complete combustion of $1.0kg$ sucrose is done, heat evloved will be:

1. $1.65\times {10}^{4}kJ$
2. $5.65\times {10}^{3}kJ$
3. $7.38\times {10}^{5}kJ$
4. $3.51\times {10}^{5}kJ$

Q.

A boy of mass 50 kg runs up a staircase of 45 steps in 9 s. If the height of each step of the staircase is 15 cm, find the power of the boy.

Q. For the combustion of $C_6{H}_{10}$ with the required amount of oxygen, which of the following is correct? (Where reactants and products are in their standard states)

1. $\Delta H>\Delta E$
2. $\Delta H=\Delta E$
3. $\Delta H<\Delta E$
4. None of these

Q. At constant T and P, which one of the following statements is correct for the reaction, $CO\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to C{O}_2\left(g\right)$

1. $\Delta H$ is independent of the physical state of the reactants of that compound
2. $\Delta H>\Delta E$
3. $\Delta H<\Delta E$
4. $\Delta H=\Delta E$

Q. When 12.0 g of carbon reacted with oxygen to form CO and $C{O}_2$ at ${25}^{\circ }C$ and constant pressure, 75.0 kcal of heat was liberated and no carbon remained. Calculate the mass of oxygen needed for it and the mole of CO and $C{O}_2$ formed.

1. $27.49g$
2. $32g$
3. $17.49g$
4. None of these

Q.

If $∆\mathrm{H}$ is the change in enthalpy and $∆\mathrm{E}$ the change in internal energy accompanying a gaseous reaction?

1. $∆\mathrm{H}$ is always greater than $∆\mathrm{E}$

2. $∆\mathrm{H}<∆\mathrm{E}$ only if the number of moles of the products is greater than the number of the reactants

3. $∆\mathrm{H}$ is always less than $∆\mathrm{E}$

4. $∆\mathrm{H}<∆\mathrm{E}$ only if the number of moles of the products is less than the number of the reactants

Q.

Internal energy and pressure for unit volume of gas are related by

A.)P=2/3E. B.)P=3/2E. C.)P=1/3E. D.)P=2E

Q. If $\Delta H$ is the change in enthalpy and $\Delta E$ the change in internal energy accompanying a gaseous reaction

1. $\Delta H<\Delta E$ only if the number of moles of the products is greater than the number of the reactants
2. $\Delta H$ is always greater than $\Delta E$
3. $\Delta H$ is always less than $\Delta E$
4. $\Delta H<\Delta E$ only if the number of moles of the products is less than the number of moles of the reactants

Q. What is the relation between $\Delta H$ and $\Delta E$ in this reaction?
$C{H}_{4\left(g\right)}+2O_{2\left(g\right)}\rightleftharpoons C{O}_{2\left(g\right)}+2H_2{O}_{\left(l\right)}$

1. 
2. 
3. 
4. 

Q. The normal boiling point of a liquid $X$ is $400\text{K}$. $△H_{\text{vap}}$ at normal boiling point is $40\text{kJ/mol}$.

1. $△S_{\text{vaporization}}<100\text{J/ mol.K at}400\text{K}\text{and}2\text{atm}$
2. $△S_{\text{vaporization}}<10\text{J/mol.K}\text{at}400\text{K}\text{and}1\text{atm}$
3. $△G_{\text{vaporization}}<0\text{at}410\text{K}\text{and}1\text{atm}$
4. $△U=43.32\text{kJ/ mol.K at}400\text{K}\text{and}1\text{atm}$