Q: A sample contains 0.5 moles of sodium chloride (NaCl). What is the mass of this sample? (Use $$M_{Na} = 22.99 g/$$mol, $$M_{Cl} = 35.45 g/$$mol)

$$0.5 \times (22.99 + 35.45) = 29.22 g$$

Q: A chemist needs to prepare 250 mL of a 0.2 M NaOH solution. How many grams of NaOH are required? ($$M_{NaOH} = 40.00 g/$$mol)

$$0.2 \times 0.250 \times 40.00 = 2.00 g$$

Q: Which of the following is the correct formula for calculating the percent composition by mass of an element in a compound?

$$\frac{\text{mass of element in 1 mol of compound}}{\text{molar mass of compound}} \times 100\%$$

Q: A gas occupies 10.0 L at 2.00 atm and 300 K. What volume will it occupy at 1.00 atm and 300 K? (Assume ideal gas behavior.)

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{2.00 \times 10.0}{1.00} = 20.0$$ L

Q: A solution is prepared by dissolving 5.00 g of glucose ($$C_6H_{12}O_6$) in enough water to make 100.0 mL of solution. What is the molarity of the solution? (M$$_{C_6H_{12}$$O_6$$} = 180.16$ g/mol)

$$\frac{5.00}{180.16 \times 0.100} = 0.277 M$$

Q: Which of the following is the correct formula for calculating the density of a substance?

$$\text{Density} = \frac{\text{mass}}{\text{volume}}$$

Question 1

Which of the following statements best describes the difference between atomic mass and molar mass?

Accepted Answer

Atomic mass is the weighted average mass of an atom in atomic mass units (amu), while molar mass is the mass of one mole of a substance in grams per mole.

Question 2

A sample contains 0.5 moles of sodium chloride (NaCl). What is the mass of this sample? (Use $$M_{Na} = 22.99 g/$$mol, $$M_{Cl} = 35.45 g/$$mol)

Accepted Answer

$$0.5 	imes (22.99 + 35.45) = 29.22 g$$

Question 3

Which of the following equations correctly relates energy, frequency, and Planck’s constant?

Accepted Answer

$$E = h 
u$$

Question 4

A chemist needs to prepare 250 mL of a 0.2 M NaOH solution. How many grams of NaOH are required? ($$M_{NaOH} = 40.00 g/$$mol)

Accepted Answer

$$0.2 	imes 0.250 	imes 40.00 = 2.00 g$$

Question 5

Which of the following is the correct balanced equation for the combustion of methane ($$CH_4) in $$oxygen?

Accepted Answer

$$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$

Question 6

Which of the following is the correct formula for calculating the percent composition by mass of an element in a compound?

Accepted Answer

$$\frac{	ext{mass of element in 1 mol of compound}}{	ext{molar mass of compound}} 	imes 100\%$$

Question 7

A gas occupies 10.0 L at 2.00 atm and 300 K. What volume will it occupy at 1.00 atm and 300 K? (Assume ideal gas behavior.)

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{2.00 	imes 10.0}{1.00} = 20.0$$ L

Question 8

Which of the following is the correct expression for the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 9

Which of the following is a correct statement about the periodic trend in atomic radius?

Accepted Answer

Atomic radius increases from top to bottom within a group.

Question 10

A solution is prepared by dissolving 5.00 g of glucose ($$C_6H_{12}O_6$) in enough water to make 100.0 mL of solution. What is the molarity of the solution? (M$$_{C_6H_{12}$$O_6$$} = 180.16$ g/mol)

Accepted Answer

$$\frac{5.00}{180.16 	imes 0.100} = 0.277 M$$

Question 11

Which of the following best describes the law of conservation of mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 12

Which of the following is the correct formula for calculating the density of a substance?

Accepted Answer

$$	ext{Density} = \frac{	ext{mass}}{	ext{volume}}$$

Question 13

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$$n = \frac{	ext{mass}}{	ext{molar mass}}$$

Question 14

A reaction produces 44.0 g of $$CO_2. $$How many moles of $$CO_2 is $$this? ($$M_{CO_2$} = 44.01 g/$$mol)

Accepted Answer

$$n = \frac{44.0}{44.01} = 1.00$$ mol

Question 15

Which of the following is the correct formula for calculating the wavelength of light given its frequency?

Accepted Answer

$$\lambda = \frac{c}{
u}$$

Question 16

Which of the following is the correct formula for calculating the percent yield of a reaction?

Accepted Answer

$$\frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100\%$$

Question 17

Which of the following is the correct formula for calculating the molarity of a solution?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

Question 18

Which of the following is the correct formula for calculating the energy of a photon given its wavelength?

Accepted Answer

$$E = \frac{hc}{\lambda}$$

Question 19

Which of the following is the correct formula for calculating the pressure of a gas using the ideal gas law?

Accepted Answer

$$P = \frac{nRT}{V}$$

Essential Reference Sheet for Introductory Chemistry

Guida di studio - Domande di pratica

Study guide - Flashcard