Chemistry Quiz 1

Heating an ore of antimony (Sb₂S₃) in the presence of iron gives the element antimony and iron (II) sulfide.

Sb₂S₃(s) + 3Fe(s) -----------> 2Sb(s) + 3FeS(s)

When 15.0g Sb₂S₃ reacts with an excess of Fe, 9.84g Sb is produced. What is the percent yield of this reaction?

• 60%

• 85.5%

• 91.5%

• 94%

If the reaction below proceeds with a 96.8% yield, how many kilograms of CaSO₄ are formed when 5.24kg SO₂ reacts with an excess of CaCO₃ and O₂?

2CaCO₃(s) + 2SO₂(g) + O₂(g) -------> 2CaSO₄(s) + 2CO₂(g)

• 12.4kg CaSO₄

• 10.7kg CaSO₄

• 11.3kg CaSO₄

• 9.65kg CaSO₄

Methanol (CH₃OH) is used in the production of many chemicals. Methanol is made by reacting carbon monoxide and hydrogen at high temperature and pressure.

CO(g) + 2H₂(g) --> CH₃OH(g)

How many moles of each reactant are needed to produce 3.60x10²g CH₃OH?

• 11.3 mole CO, 22.5 mole H₂

• 22.5 mole CO, 11.3 mole H₂

• 13.3 mole CO, 24.5 mole H₂

• 24.5 mole CO, 13.3mole H₂

Hydrazine (N₂H₄) is used as rocket fuel. It reacts with oxygen to form nitrogen and water.

N₂H₄(l) + O₂(g) --> N₂(g) + 2H₂O(g)

How many liters of N₂ (at STP) form when 1.0kg N₂H₄ reacts with 1.0kg O₂?

• 6.0x10³L N₂

• 6.5x10²L N₂

• 7.0x10³L N₂

• 7.0x10²L N₂

Hydrazine (N₂H₄) is used as rocket fuel. It reacts with oxygen to form nitrogen and water.

N₂H₄(l) + O₂(g) --> N₂(g) + 2H₂O(g)

How many grams of the excess reagent remain after the reaction?

• 5 grams

• 5.5 grams

• 4 grams

• No reagent in excess

The gas in a closed container has a pressure of 3.00 X 10²kPa at 30°C (303 K). What will the pressure be if the temperature is lowered to -172°C (101 K)?

• 1.25 X 10² kPa

• 1.25 X 10³ kPa

• 1.00 X 10² kPa

• 1.00 X 10³ kPa

Calculate the volume of a gas (in L) at a pressure of 1.00 X 10² kPa if its volume at 1.20 X 10² kPa is 1.50 X 10³ mL.

• 2.5 L

• 2.0L

• 1.8L

• 1.75 L

If 4.50g of methane gas (CH₄) is in a 2.00L container at 35°C, what is the pressure in the container?

• 4.00 X 10² kPa

• 3.55atm

• 3.95atm

• 3.60 X 10² kPa

Calculate the ratio of the velocity of helium atoms to the velocity of fluorine molecules at the same temperature.

• 1:2.25

• 2.25:1

• 4.5:2

• 2:4.5

A 3.50 L gas sample at 20°C and a pressure of 86.7kPa (0.856atm) expands to a volume of 8.00L. The final pressure of the gas is 56.7kPa (0.5597atm). What is the final temperature of the gas, in degrees Celsius?

• 300°C

• 250°C

• 170°C

• 165°C