Q: A jeweler needs 0.750 mole of silver (Ag) for a ring. If the molar mass of Ag is 107.87 g/mol, how many grams of silver are required?

$$0.750 \times 107.87 = 80.90$$ grams

Q: Which of the following is the correct conversion factor to convert grams of magnesium (Mg) to moles?

$$\frac{1\ \text{mol Mg}}{24.31\ \text{g Mg}}$$

Q: A chemist needs to prepare 5.00 moles of NaCl for an experiment. What mass of NaCl is required? (Molar mass of NaCl = 58.44 g/mol)

$$5.00 \times 58.44 = 292.2$$ grams

Q: A patient is prescribed 0.250 moles of potassium chloride (KCl) for an IV solution. If the molar mass of KCl is 74.55 g/mol, how many grams should be administered?

$$0.250 \times 74.55 = 18.64$$ grams

Q: A laboratory reaction requires 3.00 moles of magnesium. What mass of magnesium should be weighed out? (Molar mass of Mg = 24.31 g/mol)

$$3.00 \times 24.31 = 72.93$$ grams

Question 1

Which of the following best describes the role of molar mass in chemical calculations?

Accepted Answer

It is used to convert between the mass of a substance and the number of moles.

Question 2

A jeweler needs 0.750 mole of silver (Ag) for a ring. If the molar mass of Ag is 107.87 g/mol, how many grams of silver are required?

Accepted Answer

$$0.750 	imes 107.87 = 80.90$$ grams

Question 3

A box of salt contains 737 g of NaCl. If the molar mass of NaCl is 58.44 g/mol, how many moles of NaCl are present?

Accepted Answer

$$737 \div 58.44 = 12.61$$ moles

Question 4

Which of the following is the correct conversion factor to convert grams of magnesium (Mg) to moles?

Accepted Answer

$$\frac{1\ 	ext{mol Mg}}{24.31\ 	ext{g Mg}}$$

Question 5

If you have 50.0 g of magnesium (Mg), how many moles do you have? (Molar mass of Mg = 24.31 g/mol)

Accepted Answer

$$50.0 \div 24.31 = 2.06$$ moles

Question 6

A chemist needs to prepare 5.00 moles of NaCl for an experiment. What mass of NaCl is required? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$5.00 	imes 58.44 = 292.2$$ grams

Question 7

Which of the following statements about molar mass is FALSE?

Accepted Answer

Molar mass is used to convert between liters and moles of a gas at STP.

Question 8

A patient is prescribed 0.250 moles of potassium chloride (KCl) for an IV solution. If the molar mass of KCl is 74.55 g/mol, how many grams should be administered?

Accepted Answer

$$0.250 	imes 74.55 = 18.64$$ grams

Question 9

Which calculation would you use to determine the number of moles in 120 g of glucose (C$$_6H$_{12}O$_6$$), given its molar mass is 180.16 g/mol?

Accepted Answer

$$120 \div 180.16$$

Question 10

A laboratory reaction requires 3.00 moles of magnesium. What mass of magnesium should be weighed out? (Molar mass of Mg = 24.31 g/mol)

Accepted Answer

$$3.00 	imes 24.31 = 72.93$$ grams

Question 11

A nutrition label states that a serving contains 18.0 g of glucose (C$$_6H$_{12}O$_6). $$How many moles of glucose are in one serving? (Molar mass = 180.16 g/mol)

Accepted Answer

$$18.0 \div 180.16 = 0.100$$ moles

Question 12

Which of the following is the correct setup to convert 25.0 g of NaCl to moles? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$25.0 	imes \frac{1\ 	ext{mol}}{58.44\ 	ext{g}}$$

Question 13

A reaction requires 0.500 moles of magnesium. How many grams of magnesium are needed? (Molar mass = 24.31 g/mol)

Accepted Answer

$$0.500 	imes 24.31 = 12.16$$ grams

Question 14

Which of the following is NOT a correct use of molar mass?

Accepted Answer

To convert between grams and liters of a gas at STP

Question 15

A chemist has 100.0 g of NaCl. How many moles does this represent? (Molar mass = 58.44 g/mol)

Accepted Answer

$$100.0 \div 58.44 = 1.71$$ moles

Calculations Involving Molar Mass: Converting Between Mass and Moles

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