Q: A packet of artificial sweetener contains 0.0400 g of saccharin ($$C_7H_5NO_3S) $$with a molar mass of 183.18 g/mol. How many molecules of saccharin are present in the packet?

$$1.31 \times 10$$^{20}$$ molecules

Question 1

Which of the following best describes Avogadro's Number ($$N_A$$)?

Accepted Answer

The number of discrete entities (atoms, molecules, ions) in 1 mole, $$N_A = 6.022 	imes 10$$^{23}$$.

Question 2

A sample contains 4.7 g of potassium (K). What is the number of moles of potassium in the sample? (Atomic mass of K = 39.10 g/mol)

Accepted Answer

$$0.12$$ mol

Question 3

Which of the following statements about molecular and formula mass is correct?

Accepted Answer

The formula mass is the sum of the average atomic masses of all atoms in the substance's formula.

Question 4

A packet of artificial sweetener contains 0.0400 g of saccharin ($$C_7H_5NO_3S) $$with a molar mass of 183.18 g/mol. How many molecules of saccharin are present in the packet?

Accepted Answer

$$1.31 	imes 10$$^{20}$$ molecules

Question 5

Given the empirical formula $$C_2H_5O_2$$ and a molar mass of 120.10 g/mol, what is the molecular formula of the compound?

Accepted Answer

Question 6

A 100.0 g sample of a compound contains 71.1 g C and 28.9 g H. What is the empirical formula of the compound? (Atomic masses: C = 12.01 g/mol, H = 1.008 g/mol)

Accepted Answer

$$CH_4$$

Question 7

Which of the following best describes a solution?

Accepted Answer

A homogeneous mixture with uniform composition and properties throughout.

Question 8

A 355 mL soft drink contains 0.133 mol of sucrose. What is the molarity of sucrose in the beverage?

Accepted Answer

$$0.375 M$$

Question 9

Which of the following is the correct method to determine the empirical formula from percent composition?

Accepted Answer

Convert percent to grams, then to moles, divide by the smallest number of moles, and multiply to get whole numbers.

Question 10

A solution is prepared by dissolving 5.00 g of NaCl (molar mass = 58.44 g/mol) in enough water to make 250.0 mL of solution. What is the molarity of the solution?

Accepted Answer

$$0.342 M$$

Question 11

Which statement about the mole is FALSE?

Accepted Answer

A mole is the same as a gram.

Question 12

If a compound has the empirical formula $$CH_2O$$ and a molar mass of 180 g/mol, what is its molecular formula?

Accepted Answer

$$C_6H_{12}O_6$

Question 13

A liter of air contains $$9.2 	imes 10$$^{-4}$$ mol of argon. What is the mass of argon in a liter of air? (Molar mass of Ar = 39.95 g/mol)

Accepted Answer

$$0.037 g$$

Question 14

Which of the following best describes an aqueous solution?

Accepted Answer

A solution in which water is the solvent.

Question 15

What is the percent by mass of hydrogen in $$C_6H_{12}O_6$? (Atomic masses: C = 12.01, H = 1.008, O = 16.00)

Accepted Answer

$$12.0\%$$

Question 16

A compound is found to contain 40.0% C, 6.7% H, and 53.3% O by mass. What is its empirical formula?

Accepted Answer

$$CH_2O$$

Question 17

Which of the following is NOT a property of a homogeneous mixture?

Accepted Answer

Composition varies from one region to another

Question 18

How many sodium ions are present in 2.00 moles of NaCl?

Accepted Answer

$$2.41 	imes 10$$^{24}$$

Question 19

Which of the following best explains why the formula mass of an ionic compound may not be referred to as a molecular mass?

Accepted Answer

Ionic compounds do not exist as discrete molecules.

The Mole Concept, Chemical Formulas, and Solution Concentration

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