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Question: 1. What is the empirical formula of a compound tha...

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1. What is the empirical formula of a compound that is 14 g calcium, 11 g oxygen, and 0.7 g hydrogen?

CaO2H

Ca(OH)2

CaOH

Ca2OH2

2. A container of gas has a volume of 3.5 L and a pressure of 0.8 atm. Assuming the temperature remains constant, what volume of gas would result if the pressure was 0.5 atm?

2.2 L

5.6 L

0.2 L

1.8 L

3. If the temperature of an object is 335 K, how would this be expressed on the Celsius scale?

608°C

273°C

62°C

37°C

4. The mass of a quantity of NiCl2 is 24.6 g. How many formula units are in the sample?

3.2 3 1023 NiCl2 formula units

1.1 3 1023 NiCl2 formula units

5.3 3 10–21 NiCl2 formula units

1.9 3 1027 NiCl2 formula units

5. How many silver (Ag) atoms are in a silver bar that is 20.0 g?

1.1 3 1023 Ag atoms

1.8 3 1023 Ag atoms

1.3 3 1027 Ag atoms

D. 6.02 3 1023 Ag atoms

6. Which of the following devices can measure only atmospheric pressure?

Pressure gauge

Mercury tube

Tire gauge

Barometer

7. What is the major element per mass in NaOH?

Sodium

Oxygen

All elements contribute the same mass.

Hydrogen

8. What mass of propane (C3H8) is needed to produce 346 g carbon dioxide in the following reaction?

Burning of C3H8

115 g C3H8

5075 g C3H8

346 g C3H8

1.86 g C3H8

9. What mass of sulfur has to burn to produce 4.5L SO2 at 300°C and 101 kPa in the following reaction?

Burning of S

41.0 g S

3.07 g S

68.8 g S

13.5 g S

10. Which of the following is true regarding phase changes?

Condensation is the reverse of evaporation.

Freezing is the same as sublimation.

Melting is the reverse of deposition.

Sublimation is the same as boiling.

11. Theoretically, a student performing a lab experiment was expected to get 9 g of product. Instead, the student obtained only 7.8 g. What is the percent yield of the reaction performed by the student?

0.86 percent

67 percent

1.15 percent

D. 87 percent

12. What is the volume of 55 L of gas initially at 500 K and 4.25 atm when conditions change to STP?

10.5 L

428.1 L

584.0 L

127.6 L

13. How many moles are contained in a 4.67-L sample of gas at 30°C and 199 kPa?

11.8 mol

3.7 mol

1.7 mol

0.37 mol

14. At the same temperature, steam burns are often more severe than water burns because of water's high

density.

heat of vaporization.

polarity

mass.

15. A reading shows a pressure measurement of 43 in. Hg. What is the equivalent pressure in psi?

26.32 psi

2223.13 psi

21.13 psi

5.73 psi

16. According to Boyle, pressure and volume of a confined gas are _______ proportional, and according to Charles, the volume of a gas at constant pressure is _______ proportional to its Kelvin temperature.

not; inversely

directly; inversely

inversely; directly

directly; not

17. Imagine you have two containers of gas, one labeled gas A and one labeled gas B. Gas A has an average speed of 700 m/s and gas B has an average speed of 1100 m/s. Both containers are being held at the same temperature. How could you match the average speeds of gas A and gas B?

Reduce the volumes of both containers.

Lower the temperature of gas B.

Lower the temperature of gas A.

Raise the temperature of gas B.

18. The temperature of a substance _______ as its heat of fusion is added to melt the substance.

A. decreases

fluctuates from rapid increases and decreases

remains constant

increases

19. The rate of evaporation is affected by all of the following except

the temperature.

the type of solid evaporating.

the humidity.

the area of the surface.

20. All of the following conditions of STP are true except

101.3 kPa

24.2 L

273.15 K

D. 8.314

Explanation / Answer

1) What is the empirical formula of a compound that is 14 g calcium, 11 g oxygen, and 0.7 g hydrogen ?

Given that Ca = 14 g

O = 11 g

H = 0.7 g

Dividing each mass by molar mass

For Ca , 14/ 40 = 0.35

For O, 11/16 = 0.7

For H, 0.7/1 = 0.7

Divide each by smallest among them i.e. 0.35

For Ca , 0.35/0.35 = 1

For O, 0.7/ 0.35 = 2

For H, 0.7/0.35 = 2

Therefore,

Ca =1

O = 2

H = 2

Therefore,

Empirical formula = CaO2H2 = Ca(OH)2

2)  A container of gas has a volume of 3.5 L and a pressure of 0.8 atm. Assuming the temperature remains constant, what volume of gas would result if the pressure was 0.5 atm?

V1 = 3.5 L

P1 = 0.8 atm

V2 = ?

P2 = 0.5 atm

Since remains constant,

From Boyle's law P1V1 = P2V2

3.5 L x 0.8 atm = 0.5 atm x V2

V2 = 5.6 L

Therefore,

Required volume = 5.6 L

3)  If the temperature of an object is 335 K, how would this be expressed on the Celsius scale?

T = 335 K = 335 - 273 oC = 62 oC

Therefore,

Temperature in Celsius scale = 62 oC

7. What is the major element per mass in NaOH?

Molar mass of Na = 23

  Molar mass of O = 16

Molar mass of H = 1

Therefore,

major element per mass in NaOH = Na

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