Q: A student wants to convert $$0.50$$ moles of $$\mathrm{CO_2$} to $$the number of molecules. Which calculation should they use?

$$0.50 \ \mathrm{mol} \times 6.02 \times 10$$^{23}$$\ \mathrm{molecules/mol} = 3.01 \times 10$$^{23}$$\ \mathrm{molecules}$$

Question 1

Which of the following best describes the arrangement and movement of particles in a solid compared to a gas for the same substance?

Accepted Answer

Particles in a solid are closely packed and vibrate in place, while particles in a gas are far apart and move freely in all directions.

Question 2

A student is given a sample and its chemical formula is $$\mathrm{NaCl}. $$Which of the following statements is correct about this sample?

Accepted Answer

It is a compound because it contains two different elements chemically bonded together.

Question 3

Which of the following best distinguishes a pure substance from a mixture using a particle diagram?

Accepted Answer

A pure substance will show only one type of particle throughout, while a mixture will show two or more different types of particles.

Question 4

How many particles are present in one mole of any substance?

Accepted Answer

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

Question 5

A student measures the mass of a sample as $$12.34 g $$using a balance marked every $$0.01 g. $$How many significant figures should the student report in their measurement?

Accepted Answer

4

Question 6

Which of the following is the correct way to convert $$18.0$$ grams of water ($$\mathrm{H_2O}) to $$moles? (Molar mass of $$\mathrm{H_2O} is$$ $$18.0 g/$$mol)

Accepted Answer

$$\displaystyle \frac{18.0\ \mathrm{g}}{18.0\ \mathrm{g/mol}} = 1.00\ \mathrm{mol}$$

Question 7

Which of the following best describes the difference between an atom and an element?

Accepted Answer

An atom is a single particle of matter, while an element is a substance made up of only one type of atom.

Question 8

A student wants to convert $$0.50$$ moles of $$\mathrm{CO_2$} to $$the number of molecules. Which calculation should they use?

Accepted Answer

$$0.50 \ \mathrm{mol} 	imes 6.02 	imes 10$$^{23}$$\ \mathrm{molecules/mol} = 3.01 	imes 10$$^{23}$$\ \mathrm{molecules}$$

Question 9

Which of the following is the correct molar mass of $$\mathrm{C_6H_{12}O_6$} ($$glucose)? (Atomic masses: C = 12.0, H = 1.0, O = 16.0)

Accepted Answer

$$180.0\ \mathrm{g/mol}$$

Question 10

A chemical formula has a subscript of $$2$$ after the oxygen in $$\mathrm{H_2O_2}. $$What does this subscript indicate?

Accepted Answer

There are two oxygen atoms in each molecule of hydrogen peroxide.

Question 11

Which of the following is the best example of a mixture?

Accepted Answer

Air, because it contains several different gases not chemically bonded.

Question 12

A student is asked to convert $$24.0$$ grams of $$\mathrm{C} ($$carbon) to the number of atoms. (Atomic mass of C = $$12.0 g/$$mol, Avogadro's number = $$6.02 	imes 10$$^{23}$$)

Accepted Answer

$$24.0\ \mathrm{g} \div 12.0\ \mathrm{g/mol} = 2.0\ \mathrm{mol}$$; $$2.0\ \mathrm{mol} 	imes 6.02 	imes 10$$^{23}$$ = 1.20 	imes 10$$^{24}$$ atoms

Question 13

Which of the following is the most appropriate action if a chemical spill occurs during a laboratory experiment?

Accepted Answer

Alert the instructor immediately and follow their instructions.

Question 14

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule is two or more atoms bonded together, while a compound is a molecule made of different elements.

Question 15

A student is using a graduated cylinder marked every $$1 mL to $$measure a liquid. The bottom of the meniscus is between $$23 mL $$and $$24 mL. $$What is the correct way to report the measurement?

Accepted Answer

23.5 mL

Question 16

Which of the following is the correct order of steps to convert from grams to number of particles for a compound?

Accepted Answer

Grams $$\rightarrow$$ Moles $$\rightarrow$$ Particles

Question 17

Which of the following is the most important reason to wear safety goggles during a chemistry lab?

Accepted Answer

To protect your eyes from chemical splashes and flying debris.

Question 18

A student is asked to determine the molar mass of $$\mathrm{Ca(OH)_2}. ($$Atomic masses: Ca = 40.1, O = 16.0, H = 1.0)

Accepted Answer

$$40.1 + 2 	imes (16.0 + 1.0) = 74.1\ \mathrm{g/mol}$$

Question 19

Which of the following best describes how to determine the value of the markings on a measuring instrument?

Accepted Answer

Subtract the value of two adjacent markings to find the increment.

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