Enthalpy

Practice Questions

AP Chemistry › Enthalpy

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1

H2O ice melts to liquid H2O \[Heat is added\]

Which of the following is correct?

I. Δ H is positive

II. ΔS is positive

III. ΔH is negative

IV. ΔS is negative

2

Calculate ΔH for the following reaction:

CH4 (g) + O2 (g) ⇌ CO2 (g) + H2O (l)

Compound ΔH

CH4 (g) -74.8 kJ/mol

H2O (l) -285.8 kJ/mol

CO2 (g) -393.5 kJ/mol

3

Which of the following is a true statement regarding the energy involved in the formation of Methane, CH4, from graphite C(s) and H2(g) ?

4

The formation of nitrogen dioxide is a two step process.

$\small N_{2} + O_{2} \rightarrow 2NO$ $\small \Delta H = 180kJ$

$\small 2NO + O_{2}\rightarrow 2NO_{2}$ $\small \Delta H = -112kJ$

The net reaction is $\small N_{2} + 2O_{2} \rightarrow 2NO_{2}$ .

What is the change in enthalpy when creating four moles of nitrogen dioxide?

5

Which of the following statements is true concerning a chemical reaction?

6

$A \rightarrow E+F$ $\Delta H=-50kJ$

$E+F\rightarrow C+G$ $\Delta H=+85 kJ$

$B+G \rightarrow D$ $\Delta H= -10kJ$

What is the change in enthalpy for the given reaction?

$A+B\rightarrow C+D$

7

$N_{2(g)}$ $\Delta H_f=0 kJ$

$O_{2(g)}$ $\Delta H_f=0 kJ$

$\Delta H_f=90kJ$

What is the enthalpy of the following reaction?

$N_{2(g)}+O_{2(g)}\rightarrow 2NO$

8

$NO_{(g)}$ $\Delta H_f=90kJ$

$O_{2(g)}$ $\Delta H_f=0kJ$

$NO_{2}$ $\Delta H_f=33kJ$

What is the change in enthalpy for the following reaction?

$NO_{(g)}+O_{2(g)} \rightarrow NO_2$

9

$\Delta H_f=33kJ$

$O_{2(g)}$ $\Delta H_f=0kJ$

$N_{2(g)}$ $\Delta H_f=0kJ$

What is the change in enthalpy for the following reaction?

$N_{2(g)}+O_{2(g)}\rightarrow NO_2$

10

$\Delta H_f=0kJ$

$\Delta H_f=0kJ$

$\Delta H_f=-601kJ$

What is the change in enthalpy for the following reaction?

$2Mg +O_2\rightarrow 2MgO$

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