Q: How many atoms are present in 2 moles of aluminum (Al)? (Avogadro's number $$= 6.022 \times 10$$^{23}$$ atoms/mol)

$$1.2044 \times 10$$^{24}$$ atoms

Q: Which equation correctly relates mass, molar mass, and moles?

$$\text{moles} = \dfrac{\text{mass (g)}}{\text{molar mass (g/mol)}}$$

Q: A sample of aluminum (Al) weighs $$54.0 g. $$How many atoms are present in the sample? (Molar mass of Al = $$26.98 g/$$mol)

$$1.21 \times 10$$^{24}$$ atoms

Q: Which of the following statements about the mole is TRUE?

A mole is a unit that represents $$6.022 \times 10$$^{23}$$ particles.

Q: A student wants to find the number of atoms in $$0.75$$ moles of iron (Fe). What is the correct calculation?

$$0.75 \times 6.022 \times 10$$^{23}$$

Question 1

Which of the following best describes the term 'molar mass'?

Accepted Answer

The mass of one mole of a substance, measured in grams per mole.

Question 2

If you have 0.50 g of carbon (C), how many moles of carbon do you have? (Molar mass of C = 12.01 g/mol)

Accepted Answer

$$0.0416$$ moles

Question 3

Avogadro's number is used to convert between which two quantities?

Accepted Answer

Moles and atoms

Question 4

How many atoms are present in 2 moles of aluminum (Al)? (Avogadro's number $$= 6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$1.2044 	imes 10$$^{24}$$ atoms

Question 5

A student has 24.0 g of magnesium (Mg). How many moles of magnesium does the student have? (Molar mass of Mg = 24.3 g/mol)

Accepted Answer

$$0.99$$ moles

Question 6

Which equation correctly relates mass, molar mass, and moles?

Accepted Answer

$$	ext{moles} = \dfrac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$$

Question 7

A sample contains $$3.01 	imes 10$$^{23}$$ atoms of sodium (Na). How many moles of sodium are present?

Accepted Answer

$$0.5$$ moles

Question 8

Which of the following steps is necessary to convert grams of an element to number of atoms?

Accepted Answer

Divide by molar mass, then multiply by Avogadro's number.

Question 9

How many grams are in $$2.0$$ moles of sulfur (S)? (Molar mass of S = $$32.07 g/$$mol)

Accepted Answer

$$64.14 g$$

Question 10

A chemist needs $$1.20 	imes 10$$^{24}$$ atoms of copper (Cu) for an experiment. What mass of copper should be weighed out? (Molar mass of Cu = 63.55$ g/mol)

Accepted Answer

$$126.9 g$$

Question 11

Which of the following is the correct value for Avogadro's number?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Question 12

A sample of aluminum (Al) weighs $$54.0 g. $$How many atoms are present in the sample? (Molar mass of Al = $$26.98 g/$$mol)

Accepted Answer

$$1.21 	imes 10$$^{24}$$ atoms

Question 13

Which of the following statements about the mole is TRUE?

Accepted Answer

A mole is a unit that represents $$6.022 	imes 10$$^{23}$$ particles.

Question 14

A student wants to find the number of atoms in $$0.75$$ moles of iron (Fe). What is the correct calculation?

Accepted Answer

$$0.75 	imes 6.022 	imes 10$$^{23}$$

Question 15

Which of the following is the correct sequence to convert grams of an element to atoms?

Accepted Answer

Grams $$\rightarrow$$ Moles $$\rightarrow$$ Atoms

Question 16

A sample contains $$1.5$$ moles of calcium (Ca). How many grams does this sample weigh? (Molar mass of Ca = $$40.08 g/$$mol)

Accepted Answer

$$60.12 g$$

Question 17

Which of the following is NOT a correct use of Avogadro's number?

Accepted Answer

To convert grams to moles

Question 18

A chemist has $$18.0 g of $$hydrogen (H). How many moles of hydrogen does this represent? (Molar mass of H = $$1.008 g/$$mol)

Accepted Answer

$$17.86$$ moles

Question 19

Which of the following best explains why the mole is a useful unit in chemistry?

Accepted Answer

It allows chemists to count atoms and molecules by weighing substances.

Mole Concept, Molar Mass, and Avogadro's Number

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