#### Gen. chem exam 3 Flashcards

Consider a gas in a 1.0 L bulb at STP that is connected via a valve
to another bulb that is initially evacuated. Answer the following
concerning what occurs when the valve between the two bulbs is opened.
What is true about the value of ?E?

It is equal to zero.

Given the equation S(s) + O2(g) ?
SO2(g), ?H = �296 kJ, which of the
following statement(s) is (are) true? I. The reaction is
exothermic. II. When 0.500 mol sulfur is reacted, 148 kJ of
energy is released.III. When 32.0 g of sulfur are burned, 2.96 �
105 J of energy is released.

All are true.

A system receives 1275 J of heat while performing 855 J of work on
the surroundings. Calculate ?E in J.

420 J

What is the enthalpy change when 200 g of NO2 is produced
by the reaction below?2NO(g) + O2(g) =>
2NO2(g) ?H = -114. kJ

248 kJ exothermic

of heat to 1.00 g Hg

(l) will raise its
temperature by 29.9 C�. How much heat in joules (1.00 calorie =
4.184 J) will be required to raise the temperature of 14.8 g Hg

(l) from 39.6 �C to
143.9 �C?

Hint: What is the specific heat capacity of Hg(l)?

216.1 � 2%

A chemical engineer studying the properties of fuels placed 1.500 g
of a hydrocarbon in the bomb of a calorimeter and filled it with
O2 gas. The bomb was immersed in 2.500 L of water and the
reaction initiated. The water temperature rose from 20.00�C to
23.55�C. If the calorimeter (excluding the water) had a heat capacity
of 403 J/K, what was the heat of combustion (qV)
per gram of the fuel?

25.7 kJ/g

Data: 2Fe(s) + O2(g) =>
2FeO(s) ?H = -544.0 kJ 4Fe(s) +
3O2(g) =>
2Fe2O3(s) ?H = -1648.4 kJ
Fe3O4(s) => 3Fe(s) +
2O2(g) ?H = +1118.4 kJ Given the
data above, determine the heat of reaction, ?H, for the
reaction below:Reaction: Fe2O3(s)
+ FeO(s) => Fe3O4(s)

-22.2 kJ

The heat of formation of Fe2O3(s) is
-826.0 kJ/mol. Calculate the heat of the reaction below when a 27.86-g
sample of iron is reacted.
4Fe(s) +3O2(g) ---> 2Fe2O3(s)

�206.0 kJ

All of the following statements about the greenhouse effect are true except:

A and D

A sample of Kr gas is held in a cylinder with a movable piston. At
25.0oC, when the external pressure is 740 torr, the volume
of the gas is 880 mL. At what pressure will the volume change to 870
mL if the temperature is constant?

749 torr

A 13.1 L balloon is filled with H2(g) at 60.13
oC producing a pressure of 1.23 atm. Assuming that the
balloon can expand or contract over a sufficient range of volume, what
is its volume in L when the temperature is 146.9 oC and the
pressure is 1,642 torr? Enter your answer with two decimal places and
no units.

9.40 � 2%

Consider the reaction between hydrogen gas and nitrogen gas to form
ammonia:3 H2(g) + N2(g) => 2
NH3(g) How many grams of ammonia could be produced by
the reaction of 6.00 liters of hydrogen with 4.00 liters of nitrogen
at STP?

3.04 g NH3

A sample of 0.186 g of an ideal gas occupies 0.750 L at STP. What is
the molar mass of the gas?

5.56

A gas mixture, with a total pressure of 300. torr, consists of equal masses of Ne and
Ar. What is the partial pressure of Ne, in torr?
Hint: What is the mole fraction of Ne?

200

Four identical 1.0-L flasks contain the gases He, Cl2,
CH4, and NH3, each at 0�C and 1 atm pressure.
For which gas do the molecules have the highest average velocity?

He

Butane, C4H10, will behave most like an ideal gas:

at high temperature and low pressure

Which best explains the following trend?
Element b.p. (K) He 4 Ne 25 Ar 95 Kr 125 Xe 170

none of these

If a metal crystallizes in a primitive cubic lattice, each metal atom
has ____ nearest neighbor atoms of the same kind.

6

Which one of the following properties is least characteristic of
typical metals?

brittleness