CHEMISTRY 121 WORKSHEET CH #9&10 FEBRUARY 03, 2015

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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

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