CHEMISTRY 121
WORKSHEET CH #9&10
FEBRUARY 03, 2015
ΔE=q+w,
1.
A student combines 5.66 grams of zinc with 9.33 g of hydrochloric acid. a.
Write a balanced equation
Zn + 2 HCl ZnCl
2
+ H
2 b.
Determine the mass of hydrogen produced
5.66 gZn mole Zn
65.38 g mole H
2 mole Zn
2.018g H
2 mole H
2
= 0.175 g H
2
9.33 g HCl mole HCl mole H
2
2.018 g H
35.45 g HCl 2 mole HCl mole H
2
2 c.
Which reactant is in excess?
= 0.266 g H
2
HCl d.
What is the percent yield if 1.44 g of hydrogen is produced?
1.44 g
0.175 g
X 100 = 823 %
2.
Alcohol component of gasoline burns by a combustion equation. Assume the formula is C
2
H
6
O for this alcohol and 833 kJ is released in the process. a.
Write a balanced thermochemical equation
C
2
H
6
O + 3 O
2
2 CO
2
+ 3 H
2
O ΔH = - 833 kJ b.
How much energy is released when 5.66 g of water is produced?
5.66 g H
2
O mole H
2
O
18.02 g H
2
O
833 kj
3 mole H
2
O
= 87.2 kj
3.
A system releases 125 J of heat, and 104 kj of work is done on the system. Calculate ΔE.
ΔE = q + w = -0.125 kj + 104 kj = 104 kj
4.
If 125 j of heat energy is applied to a block of silver weighing 29.3 g, by how much will the temperature increase in degrees Celsius? The specific heat of silver is 0.24 j/g-°C. g-°C
0.24 j
125 j
29.3 g
= 17.8 °C
5.
Given the following data:
S( s ) + 3/2 O
2
( g ) SO
3
( g ) ΔH = -395.2 kj
2SO
2
( g ) + O
2
( g ) 2SO
3
( g ) ΔH = -198.2 kj
Calculate ΔH for the reaction S( s ) +O
2
( g ) SO
3
( g )
2S( s ) + 3 O
2
( g ) 2 SO
3
( g ) ΔH = 2(-395.2) kj
2SO
3
( g ) 2SO
2
( g ) + O
2
( g
) ΔH = +198.2 kj
2 S + 3 O
2
+ 2 SO
2 S + 2 O
3
2 SO
2
3
2SO
+ 2SO
2
2
+ O
2
ΔH = -592.2 kj
ΔH = -592.2 kj
S + O
2
SO
2
ΔH = 296.1 kj