Q: A sample contains $$3.01 \times 10$$^{23}$$ molecules of $$\mathrm{$$CO_2$$}$$. What is the mass of this sample? (Molar mass of $$\mathrm{$$CO_2$$}$$ is 44$$~\mathrm{g/mol}$$)

$$0.5~\mathrm{mol} \times 44~\mathrm{g/mol} = 22~\mathrm{g}$$

Q: A chemist needs $$0.25~\mathrm{mol} of$$ $$\mathrm{NaCl}$$ for an experiment. What mass of $$\mathrm{NaCl}$$ should be weighed out? (Molar mass of $$\mathrm{NaCl} is$$ $$58.5~\mathrm{g/mol})$$

$$0.25~\mathrm{mol} \times 58.5~\mathrm{g/mol} = 14.625~\mathrm{g}$$

Q: Which of the following is the correct relationship between moles, mass, and molar mass?

$$\text{Moles} = \dfrac{\text{Mass}}{\text{Molar Mass}}$$

Q: Which of the following best describes the relationship between the mole and Avogadro's number?

One mole contains $$6.022 \times 10$$^{23}$$ particles.

Question 1

Which of the following best describes a mole in chemistry?

Accepted Answer

A unit representing the number of atoms or molecules, specifically $$6.022 	imes 10$$^{23}$$ entities.

Question 2

If you have 18 grams of water ($$\mathrm{H_2O}$$), how many moles of water do you have? (Molar mass of $$\mathrm{H_2O} is$$ $$18~\mathrm{g/mol})$$

Accepted Answer

$$1~\mathrm{mol}$$

Question 3

Which of the following statements about Avogadro's number is correct?

Accepted Answer

It is the number of particles in one mole of a substance, equal to $$6.022 	imes 10$$^{23}$$.

Question 4

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of $$\mathrm{$$CO_2$$}$$. What is the mass of this sample? (Molar mass of $$\mathrm{$$CO_2$$}$$ is 44$$~\mathrm{g/mol}$$)

Accepted Answer

$$0.5~\mathrm{mol} 	imes 44~\mathrm{g/mol} = 22~\mathrm{g}$$

Question 5

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 them.

Question 6

How many atoms are present in $$2~\mathrm{mol} of $$sodium ($$\mathrm{Na}$$)?

Accepted Answer

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

Question 7

A chemist needs $$0.25~\mathrm{mol} of$$ $$\mathrm{NaCl}$$ for an experiment. What mass of $$\mathrm{NaCl}$$ should be weighed out? (Molar mass of $$\mathrm{NaCl} is$$ $$58.5~\mathrm{g/mol})$$

Accepted Answer

$$0.25~\mathrm{mol} 	imes 58.5~\mathrm{g/mol} = 14.625~\mathrm{g}$$

Question 8

Which of the following is the correct relationship between moles, mass, and molar mass?

Accepted Answer

$$	ext{Moles} = \dfrac{	ext{Mass}}{	ext{Molar Mass}}$$

Question 9

A patient is given $$0.9~\mathrm{g} of $$sodium chloride ($$\mathrm{NaCl}) in a $$saline solution. How many moles of $$\mathrm{NaCl}$$ does this represent? (Molar mass of $$\mathrm{NaCl} is$$ $$58.5~\mathrm{g/mol})$$

Accepted Answer

$$0.015~\mathrm{mol}$$

Question 10

Which of the following best describes the term 'atomic mass unit' (amu)?

Accepted Answer

The mass of a single atom of carbon-12 divided by 12.

Question 11

A sample of magnesium contains $$4.8~\mathrm{g}. $$How many atoms of magnesium are present? (Molar mass of $$\mathrm{Mg} is$$ $$24~\mathrm{g/mol})$$

Accepted Answer

$$1.2044 	imes 10$$^{23}$$

Question 12

Which of the following is a correct application of the mole concept in a real-world scenario?

Accepted Answer

Calculating the number of molecules in a given mass of glucose for a medical IV solution.

Question 13

If $$1~\mathrm{mol} of$$ $$\mathrm{O_2$}$$ gas occupies $$22.4~\mathrm{L} at $$standard temperature and pressure (STP), how many liters will $$0.5~\mathrm{mol} of$$ $$\mathrm{O_2$}$$ occupy at STP?

Accepted Answer

$$11.2~\mathrm{L}$$

Question 14

A student dissolves $$5~\mathrm{g} of $$glucose ($$\mathrm{C_6H_{12}O_6$}) in $$water. What is the number of molecules present in the solution? (Molar mass of glucose is $$180~\mathrm{g/mol})$$

Accepted Answer

$$1.67 	imes 10$$^{22}$$

Question 15

Which of the following is the best explanation for why atomic masses on the periodic table are not whole numbers?

Accepted Answer

They represent the average mass of all isotopes of an element, weighted by their natural abundance.

Question 16

A reaction requires $$0.1~\mathrm{mol} of$$ $$\mathrm{H_2SO_4}. $$What mass of $$\mathrm{H_2SO_4} is $$needed? (Molar mass of $$\mathrm{H_2SO_4} is$$ $$98~\mathrm{g/mol})$$

Accepted Answer

$$9.8~\mathrm{g}$$

Question 17

Which of the following best describes the relationship between the mole and Avogadro's number?

Accepted Answer

One mole contains $$6.022 	imes 10$$^{23}$$ particles.

Question 18

A chemist has $$12~\mathrm{g} of $$carbon-12. How many atoms does this sample contain?

Accepted Answer

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

Question 19

Which of the following is the correct calculation for the number of moles in $$50~\mathrm{g} of$$ $$\mathrm{$$CaCO_3$$}$$? (Molar mass of $$\mathrm{$$CaCO_3$$} is$$ $$100~\mathrm{g/mol})$$

Accepted Answer

$$0.5~\mathrm{mol}$$

Mole Concept and Chemical Composition: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards