Thermodynamics Test

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Thermodynamics Test - 69

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Weekly Quiz Competition

Question 1
1 / -0

For a non-spontaneous reaction, at $${30}^{o}C$$, $$\Delta H> 0$$ and $$\Delta S> 0$$. The reaction becomes spontaneous by?

A
Decreasing temperature

B
Increasing temperature

C
Maintaining temperature constant

D
Does not maintain temperature

Solution
Question 2
1 / -0

Ethyl chloride ($${C}_{2}{H}_{5}Cl$$) is prepared by reaction of ethylene with hydrogen cloride:
$${C}_{2}{H}_{4}(g)+Hcl(g)\rightarrow {C}_{2}{H}_{5}Cl(g)$$; $$\Delta H=-72.3kJ$$
What is the value of $$\Delta E$$ (in kJ), if $$70g$$ of ethylene and $$73g$$ of $$HCl$$ are allowed to react at $$300K$$

A
$$-69.8$$

B
$$-180.75$$

C
$$-174.5$$

D
$$-139.6$$

Solution
Question 3
1 / -0

$$\Delta S$$ for $$4Fe(s)+3{O}_{2}(s)\rightarrow 2{Fe}_{2}{O}_{3}(s)$$ is $$-550J/mol/K$$. The process is found to be spontaneous even at $$298K$$ because ($$\Delta H=-1650kJ$$)

A
$$\Delta {S}_{total}=-2000J$$

B
$$\Delta {S}_{total}=+1650J$$

C
$$\Delta {S}_{total}=+4980J$$

D
$$\Delta {S}_{total}=-4980J$$

Solution
Question 4
1 / -0

In which of the following case entropy decreases-

A
Solid changing to liquid

B
Expansion of a gas

C
Crystals dissolve

D
Polymerisation

Solution
Question 5
1 / -0

For a reaction $${R}_{1},\Delta G=x KJ {mol}^{-1}$$. For a reaction $${R}_{2},\Delta G=y$$ $$KJ{mol}^{-1}$$. Reaction $${R}_{1}$$ is non spontaneous but along with $${R}_{2}$$ it is spontaneous. This means that:

A
$$x$$ is $$-ve$$, $$y$$ is $$+ve$$ but in magnitude $$x> y$$

B
$$x$$ is $$-ve$$, $$y$$ is $$+ve$$ but in magnitude $$y> x$$

C
Both $$x$$ and $$y$$ are $$-ve$$ but not equal

D
Both $$x$$ and $$y$$ are $$+ve$$ but not equal

Solution
Question 6
1 / -0

An equilibrium reaction $$X+Y \rightleftharpoons W+Z, \triangle H=+ve $$ is spontaneous in the forward direction. Then corresponding sign of $$\triangle G$$ and $$\triangle S $$ should be respectively:

A
+ve, -ve

B
-ve , +ve

C
+ve , +ve

D
-ve , -ve
Question 7
1 / -0

Rank the following substances in order of decreasing heat of combusion (maximum $$\to$$ minimum).

A
$$1 > 2 > 4 > 3$$

B
$$3 > 4 > 2 > 1$$

C
$$2 > 4 > 1 > 3$$

D
$$1 > 3 > 2 > 4$$

Solution
Question 8
1 / -0

Consider the reaction:

$$4 NO_{2(g)} + O_{2(g)} \rightarrow 2 N_2O_{5(g)} ; \, \, \, \Delta_rH = -111 kJ$$

If $$N_2O_{5(s)}$$ is formed instead of $$N_2O_{5(g)}$$ in the above reaction, then $$\Delta_rH $$ value will be:
[Given, $$\Delta H$$ of sublimation for $$N_2O_5$$ is $$54 \, kJ \, mol^{-1}$$]

A
$$+ 54\ kJ$$

B
$$+ 219\ kJ$$

C
$$-219\ kJ$$

D
$$-165\ kJ$$

Solution

$$4 {N{O}_{2}}_{\left( g \right)} + {{O}_{2}}_{\left( g \right)} \longrightarrow 2 {{N}_{2}{O}_{5}}_{\left( g \right)}; \quad \Delta{H} = -111 \; kJ ..... \left( 1 \right)$$

$${{N}_{2}{O}_{5}}_{\left( s \right)} \longrightarrow {{N}_{2}{O}_{5}}_{\left( g \right)}; \quad \Delta{H} = 54 \; kJ$$

$${{N}_{2}{O}_{5}}_{\left( g \right)} \longrightarrow {{N}_{2}{O}_{5}}_{\left( s \right)}; \quad \Delta{H} = -54 \; kJ$$

$$2 \times \left[ {{N}_{2}{O}_{5}}_{\left( g \right)} \longrightarrow {{N}_{2}{O}_{5}}_{\left( s \right)}; \quad \Delta{H} = -54 \; kJ \right]$$

$$2 {{N}_{2}{O}_{5}}_{\left( g \right)} \longrightarrow 2 {{N}_{2}{O}_{5}}_{\left( s \right)}; \quad \Delta{H} = -108 \; kJ ..... \left( 2 \right)$$

Adding $${eq}^{n} \left( 1 \right) \& \left( 2 \right)$$, we have

$$4 {N{O}_{2}}_{\left( g \right)} + {{O}_{2}}_{\left( g \right)} + 2 {{N}_{2}{O}_{5}}_{\left( g \right)} \longrightarrow 2 {{N}_{2}{O}_{5}}_{\left( g \right)} + 2 {{N}_{2}{O}_{5}}_{\left( s \right)}; \quad \Delta{H} = \left[ \left( -111 \right) + \left( -108 \right) \right] \; kJ$$

$$4 {N{O}_{2}}_{\left( g \right)} + {{O}_{2}}_{\left( g \right)} \longrightarrow 2 {{N}_{2}{O}_{5}}_{\left( s \right)}; \quad \Delta{H} = -219 \; kJ$$

Hence if $${{N}_{2}{O}_{5}}_{\left( s \right)}$$ is formed instead of $${{N}_{2}{O}_{5}}_{\left( g \right)}$$, the value of $$\Delta{H}$$ will be $$-219 \; kJ$$.
Question 9
1 / -0

In an insulated container 1 mole of a liquid. molar volume 100 ml at 1 bar. Liquid is steeply taken to 100 bar, when volume of liquid decreases by 1 ml. Find $$\Delta H$$ for the process.

A
7900 bar mL

B
8900 bar mL

C
9900 bar mL

D
10900 bar mL

Solution
Question 10
1 / -0

the above reaction was carried out at 300 K in a bomb calorimeter. The heat released was 743 kJ/mol. The value of $$\triangle H_{300K}$$ for this reaction would be:

A
-740.5 kJ/mol

B
-741.75 kJ/mol

C
-743.0 kJ/mol

D
-744.25 kJ/mol

Solution