Wayground logo

Free Printable Worksheets

Font size

S
M
L
XL
Worksheets

7.6 Hess's Law

Total questions: 14

Worksheet time: 4hrs 30mins

Name
Class
Date
1.

Using the equations below:

C(s) + O2(g) → CO2(g) ∆H = –390 kJ

Mn(s) + O2(g) → MnO2(s) ∆H = –520 kJ

what is ∆H (in kJ) for the following reaction?

MnO2(s) + C(s) → Mn(s) + CO2(g)

a)

910

b)

130

c)

-130

d)

-910

2.

Using the equations below

Cu(s) + 1/2O2(g) → CuO(s) ∆H = –156 kJ

2Cu(s) + O2(g) → Cu2O(s) ∆H = –170 kJ

what is the value of ∆H (in kJ) for the following reaction?

2CuO(s) → Cu2O(s) + 1/2O2(g)

a)

142

b)

15

c)

-15

d)

-142

3.

Consider the following equations.

Mg(s) + O2(g) → MgO(s) ∆H = –602 kJ

H2(g) + O2(g) → H2O(g) ∆H = –242 kJ

What is the ∆H value (in kJ) for the following reaction?

MgO(s) + H2(g) → Mg(s) + H2O(g)

a)

-844

b)

-360

c)

+360

d)

+844

4.

The following equations show the oxidation of carbon and carbon monoxide to carbon dioxide.

C(s) +O2(g) → CO2(g) ΔH = –x kJ mol–1

CO(g) + O2(g) → CO2(g) ΔH = –y kJ mol–1

What is the enthalpy change, in kJ mol–1, for the oxidation of carbon to carbon monoxide?

C(s) + O2(g) → CO(g)

a)

x + y

b)

-x - y

c)

y - x

d)

x - y

5.
In an endothermic reaction the system is releasing energy.
a)
True
b)
False
c)
Sometimes
6.
In an exothermic reaction, heat is ...
a)
taken in
b)
given out
c)
nothing happens
d)
it gets colder
7.

A chemical reaction that requires energy is a(n)

a)
exothermic reaction 
b)
endothermic reaction 
c)
over reaction 
d)
redox reaction
8.

The enthalpies of combustion of C(s), H2(g) and C4H9OH(l) (in kJmol-1) are as follows   C(s) + O2(g)   --->  CO2(g)   ∆H=a H2(g) + ½O2(g)   --->   H2O(l)  ∆H=b C4H9OH(l) + 6O2(g)   --->   4CO2(g) + 5H2O(l)  ∆H=c

What is the enthalpy change for the reaction shown below?   4C(g) + 5H2(l) + ½O2(g)   --->   C4H9OH(l)

a)
c – 4a – 5b
b)
2a + 10b - c
c)
4a + 5b - c
d)
2a + 5b + c
9.

If N2 (g) + 2O2 (g) ⟶\longrightarrow   2NO2(g) has a ΔHrxn \Delta H_{rxn\ }  = 68, then what is the ΔHrxn\Delta H_{rxn}  if you reverse the reaction?

a)

86 kJ

b)

- 86 kJ

c)

68 kJ

d)

-68 kJ

10.

How much energy is required to turn 1 mole of N2O4(g) into 2 moles N & 4 moles O(g)?

a)

1933 kJ

b)

-1875 kJ

c)

- 1933 kJ

d)

1875 kJ

11.
a)
-804.6
b)
-202.3
c)
-296.1
d)
-233.0
12.
a)
-233
b)
-11.3
c)
-805
d)
-226
13.
a)
-296.1
b)
226
c)
-11
d)
255.95
14.
a)
226
b)
255
c)
233
d)
11.3