Q: How many molecules are present in 0.250 mol of water ($$\mathrm{H_2O}$$)?

$$1.51 \times 10$$^{23}$$ molecules

Q: Calculate the number of hydrogen atoms in 0.350 mol of fructose ($$\mathrm{C_6H_{12}O_6$}).$$

$$2.53 \times 10$$^{24}$$ H atoms

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

A mole is the amount of substance containing $$6.022 \times 10$$^{23}$$ particles.

Q: Which conversion factor would you use to convert grams of a substance to number of molecules?

$$\frac{1 \text{ mol}}{\text{molar mass (g)}}$$ then $$\frac{6.022 \times 10$$^{23}$$ \text{ molecules}}{1 \text{ mol}}$$

Q: A chemist has 0.500 mol of $$\mathrm{N_2$}$$ gas. How many molecules of $$\mathrm{N_2$}$$ are present?

$$3.01 \times 10$$^{23}$$ molecules

Q: How many oxygen atoms are present in 2.00 mol of $$\mathrm{H_2O}$$?

$$1.20 \times 10$$^{24}$$ atoms

Q: A balloon is filled with 28.01 grams of nitrogen gas ($$\mathrm{N_2$}). $$How many molecules of $$\mathrm{N_2$}$$ are present?

$$6.02 \times 10$$^{23}$$ molecules

Question 1

Which of the following best defines Avogadro's number?

Accepted Answer

The number of atoms or molecules in one mole of a substance.

Question 2

How many molecules are present in 0.250 mol of water ($$\mathrm{H_2O}$$)?

Accepted Answer

$$1.51 	imes 10$$^{23}$$ molecules

Question 3

A sample contains $$3.28 	imes 10$$^{11}$$ molecules of methanol. How many moles of methanol does this represent?

Accepted Answer

$$5.45 	imes 10$$^{-13}$$ mol

Question 4

Calculate the number of hydrogen atoms in 0.350 mol of fructose ($$\mathrm{C_6H_{12}O_6$}).$$

Accepted Answer

$$2.53 	imes 10$$^{24}$$ H atoms

Question 5

What is the molar mass of sodium chloride ($$\mathrm{NaCl}$$)?

Accepted Answer

$$58.443 g/$$mol

Question 6

If you have 213 grams of sodium chloride, how many moles do you have? ($$\mathrm{NaCl}$$ molar mass = $$58.443 g/$$mol)

Accepted Answer

$$3.65$$ mol

Question 7

Which of the following statements about the mole is correct?

Accepted Answer

A mole is the amount of substance containing $$6.022 	imes 10$$^{23}$$ particles.

Question 8

How many atoms are in 6.8 mol of gold?

Accepted Answer

$$4.1 	imes 10$$^{24}$$ atoms

Question 9

Which conversion factor would you use to convert grams of a substance to number of molecules?

Accepted Answer

$$\frac{1 	ext{ mol}}{	ext{molar mass (g)}}$$ then $$\frac{6.022 	imes 10$$^{23}$$ 	ext{ molecules}}{1 	ext{ mol}}$$

Question 10

A chemist has 0.500 mol of $$\mathrm{N_2$}$$ gas. How many molecules of $$\mathrm{N_2$}$$ are present?

Accepted Answer

$$3.01 	imes 10$$^{23}$$ molecules

Question 11

Which of the following is true about the relationship between atomic mass units (amu) and molar mass?

Accepted Answer

The atomic mass in amu is numerically equal to the molar mass in grams per mole.

Question 12

How many oxygen atoms are present in 2.00 mol of $$\mathrm{H_2O}$$?

Accepted Answer

$$1.20 	imes 10$$^{24}$$ atoms

Question 13

A patient receives 79.55 grams of copper(II) oxide ($$\mathrm{CuO}) $$during a medical procedure. How many moles of $$\mathrm{CuO} is $$this?

Accepted Answer

$$1.00$$ mol

Question 14

Which of the following best describes the process for converting from number of atoms to mass in grams?

Accepted Answer

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

Question 15

A balloon is filled with 28.01 grams of nitrogen gas ($$\mathrm{N_2$}). $$How many molecules of $$\mathrm{N_2$}$$ are present?

Accepted Answer

$$6.02 	imes 10$$^{23}$$ molecules

Question 16

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

Accepted Answer

To convert grams directly to number of atoms without using molar mass.

Question 17

A sample contains $$1.204 	imes 10$$^{24}$$ $$\mathrm{N}$$ atoms. How many moles of $$\mathrm{N}$$ does this represent?

Accepted Answer

$$2.00$$ mol

Question 18

Which of the following compounds has the greatest molar mass?

Accepted Answer

$$\mathrm{CuO}$$

Question 19

A chemist needs $$2.00 	imes 10$$^{24}$$ molecules of water for an experiment. How many moles of water should they use?

Accepted Answer

$$3.32$$ mol

Question 20

Which of the following is the correct sequence for converting grams to number of atoms?

Accepted Answer

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

Avogadro’s Number, Moles, and Molar Mass: Foundations for Counting Atoms and Molecules

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