# Chemistry Questions

a. small whole number ratios

b. atmospheric pressure

c. inverse

d. 14.7

1………Normal air pressure

2………volumes of gases always combine with each other in this relationship.

3………Less at the top of the mountain than at the bottom of the mountain.

4……… Gas volume and gas pressure have this relationship.

b. atmospheric pressure 1………Normal air pressure

a. small whole number ratios 2………volumes of gases always combine with each other in this relationship.

d. 14.7 3………Less at the top of the mountain than at the bottom of the mountain.

c. inverse 4……… Gas volume and gas pressure have this relationship.

2.

a. states that submicroscopic particles are in constant, random motion

b. increased kinetic energy of particles

c. occurs only at the surface of a liquid

d. formation of dew on grass in the morning

5………evaporation

6……….increased temperature

7……….kinetic theory

8……….condensation

7……….kinetic theory a. states that submicroscopic particles are in constant, random motion

6……….increased temperature b. increased kinetic energy of particles

5………evaporation c. occurs only at the surface of a liquid

8……….condensation d. formation of dew on grass in the morning

3.

a. Flows but has definite volume

b. state of matter that is easily compressible

c. For water, 0 degrees C

d. vapor pressure = atmospheric pressure

9……..gas

10…….freezing point

11……..liquid

12……..boiling

11……..liquid a. Flows but has definite volume

9……..gas b. state of matter that is easily compressible

10…….freezing point c. For water, 0 degrees C

12……..boiling d. vapor pressure = atmospheric pressure

4.

Volumes of gases always combine with each other in this relationship.

a. pounds per square inch

b. small whole number ratios

c. large whole number rations

d. pounds per cubic inch

5.

The process of sublimation is the reason for which of the following? a. dry ice melts

b. water is able to freeze

c. ice remains frozen

d. food stored in a freezer becomes freezer burned

6.

At 525 mm Hg and 85 degrees C, the volume of a sample of nitrogen gas is 26.8 L. What is the volume at STP.

a. 1L

b. 10.9L

c. 15.3L

d. 15.3 L

The general equation of the gasses in a transformation from 1 to 2 writes as

$P1*V1/ T1 =P2*V2/T2$ where $P$ is the pressure of the gas, $V$ the volume and $T$ the absolute temperature

STP is $T = 300 K$ (27 Celsius) and $P = 760 mm$ Hg (1 atmosphere)

$V2 =(P1/P2)*(T2/T1)*V1 =525/760 *300/(273+85) *26.8 =15.5 liter$

7.

When .500 mole of sodium is produced according to the reaction 2NaN3 → 3N2 + 2Na. how many moles of nitrogen as are also produced?

a. .750 moles

b. 1.5 moles

c. 2 moles

d. 3 moles

according to the equation

3 mole N2 …….2 mole Na

x ………………0.5 mole Na

$x =3*0.5/2 =0.750$ moles.

The correct choice is a)

8.

A cylinder of compressed gas has a volume of $3.85 L$ and a pressure of $463 kPa$. What volume would the gas occupy if it were allowed to escape into a balloon at a pressure of $110 kPa$? Assume constant temperature.

a. 11.5 L

b. 16.2 L

c. 22.4 L

d. 28.9 L

The law of the transformation of a gas under the same temperature is

$P1*V1 =P2*V2$

Hence $V2 =P1*V1/P2 =463*3.85/110 =16.205$ liter

Correct choice is b

A cylinder contains 6.94 L of gas at a temperature of 15 degrees C. The cylinder is heated, and a piston moves in the cylinder so that constant pressure is maintained, If the final volume of the gas in the cylinder is 8.5 L. what is the final temperature/

a. 12.2 C

b. 38 C

c. 54 C

d. 80 C

The law of the transformation of a gas under the same pressure is

$V1/T1 =V2/T2$ where T is the absolute temperature.

Hence $T2 = V2 *T1/V1 =8.5*(273+15)/6.94 =352.74 K = 79.74$ Celsius

The correct choice is d)

10.

A 2.16 L sample of oxygen is collected at 99.6 kPa and 305 K. If the pressure increases to 122.8 kPa and the temperature drops to 285. K. what volume will the oxygen occupy?

a. .55 L

b. 1.64 L

c. 3.8 L

d. 5.5 L

The law of a general transformation of a perfect gas between states 1 and 2 is

$P1*V1/T1 =P2*V2/T2$

$V2 =(P1/P2) *(T2/T1) *V1 =(99.6/122.8)* (285/305) *2.16 =1.64 liter$

The correct choice is b)

11.

What is the molar mass of ammonium sulfate?

a. 66.14 g

b. 100.49 g

c. 114.07 g

d. 132. 16 g

$M ((NH4)2SO4) =2*(14+4) +32 +4*16 =132$

Correct choice is d)

What is the number of moles represented by 38.1 g of FeCI3?

a. .235 mol

b. 4.25 mol

c. 38.1 mol

d. 162.2 mol

$M (FeCl3) = 56 +35.5*3 =162.5$

Number of moles $= 38.1/162.5 =0.234$ moles

Correct choice is a)

13.

Hydrogen gas reacts with copper (II) oxide to form copper metal and water vapor according to the reaction: CuO + H2 → Cu + H2O. What mass of copper is produced if 255 L of hydrogen at STP are used up in this reaction?

a. 258 g

b. 472 g

c. 723 g

d. 905 g

$P*V = n*R*T$ where n is the number of moles and R the gas constant (=8310 J/mol/K)

STP is $T = 273 k and P = 10^5 N/m^2$

$n= p*v/R/T= 10^5 *0.255/8310/273 =0.011$ mol $H_2$

1mol $H_2$ ……1 mol Cu

0.011 mol $H_2$ …..0.011 mol Cu

Cu mass $= M(Cu) *0.01 =65.5*0.011 =0.730 g$

correct choice is c)

14.

Calculate the mass of precipitate that forms when 300 mL of an aqueous solution containing 67.0g of silver nitrate reacts with excess sodium chloride solution by the following reaction:

AgNO3(aq) + NaCI(aq) → NaNO3(aq) + AgCI(s)

a. 45.9 g

b. 56.5 g

c. 63.7 g

d. 72.4 g

answer

$M(AgNO3) =108 +14+3*16 = 170$

$M(AgCl) =108+35.5 =143.5$

170 g AgNO3 …………143.5 g AgCl

67 g AgNO3 …………x

$x =67*143.5/170 =56.56 g$

correct choice is b)

15.

What is the volume of .625 mol of nitrogen at 74.2 kPa and 85 degrees C?

a. 9.2 L

b. 16.8 L

c. 25.1 L

d. 37. 4 L

answer

The law of general gases is

$P*V =n*R*T$ where R is the constant of gases (8310 J/(mol*K))

$V = n*R*T/P =0.625*8310*(273+85)/(74.2*10^3) =25.1 L$

correct choice is c)