$$6.00 \times 6.022 \times 10$$^{23}$$

A mole is the mass of a substance that contains $$6.022 \times 10$$^{23}$$ particles, measured in grams.

Question 1

Which of the following best defines Avogadro's Number?

Accepted Answer

The number of particles in exactly 12 grams of carbon-12, which is $$6.022 	imes 10$$^{23}$$.

Question 2

A laboratory sample contains $$1.204 	imes 10$$^{24}$$ molecules of H_2$O. How many moles of water does this sample contain?

Accepted Answer

$$2.00$$ moles

Question 3

What is the mass of $$2.50$$ moles of NaCl? (Molar mass of NaCl = $$58.45 g/$$mol)

Accepted Answer

$$146.1 g$$

Question 4

Which of the following statements about the mole is correct?

Accepted Answer

A mole is the amount of substance that contains as many particles as there are in exactly 12 grams of $$^{12}C.$$

Question 5

How many oxygen atoms are present in $$3.00$$ moles of H$$_2O$$?

Accepted Answer

$$6.00 	imes 6.022 	imes 10$$^{23}$$

Question 6

A red balloon contains $$32.0 g of O$_2$$ gas. How many molecules of O$$_2$$ are in the balloon?

Accepted Answer

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

Question 7

Which of the following is the correct relationship between the mass of a single H$$_2O $$molecule and a mole of H$$_2O$$?

Accepted Answer

1 molecule H$$_2O $$has a mass of $$18.0$$ amu, and 1 mole H$$_2O $$has a mass of $$18.0 g$$

Question 8

If you have $$9.00 g of H$_2O$$, how many moles do you have?

Accepted Answer

$$0.500$$ moles

Question 9

Which of the following best explains why chemists use the mole as a counting unit?

Accepted Answer

Because atoms and molecules are too small to count individually, and the mole allows chemists to relate mass to number of particles.

Question 10

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of CO_2$. What is the mass of this sample? (Molar mass of CO_2$ = 44.0$ g/mol)

Accepted Answer

$$22.0 g$$

Question 11

Which of the following is true about the number of particles in a mole of different substances?

Accepted Answer

A mole of any substance contains the same number of particles, $$6.022 	imes 10$$^{23}$$.

Question 12

If you have $$58.45 g of $$NaCl, how many formula units of NaCl do you have?

Accepted Answer

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

Question 13

Which of the following is the best description of a mole in terms of laboratory measurements?

Accepted Answer

A mole is the mass of a substance that contains $$6.022 	imes 10$$^{23}$$ particles, measured in grams.

Question 14

How many moles of O$$_2$$ are present in $$64.0 g of O$_2$$?

Accepted Answer

$$2.00$$ moles

Question 15

A chemist needs $$3.01 	imes 10$$^{23}$$ molecules of H_2$O for an experiment. What mass of water should she use?

Accepted Answer

$$9.00 g$$

The Mole and Chemical Formula Relationships: Study Notes for Introductory Chemistry

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