Q: How many molecules are present in 36.0 g of water ($$H_2O$$)? (Molar mass $$H_2O = 18.0 g/$$mol, Avogadro's number $$= 6.022 \times 10$$^{23}$$ molecules/mol)

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

Question 1

Which of the following best describes the difference between a mixture and a compound, as illustrated by hydrogen and oxygen gases versus water?

Accepted Answer

A compound has a fixed ratio of elements chemically bonded, while a mixture can have any ratio and the elements are not chemically bonded.

Question 2

Which of the following is the correct empirical formula for glucose, $$C_6H_{12}O_6$?

Accepted Answer

$$CH_2O$$

Question 3

Which of the following statements about ionic and covalent bonds is correct?

Accepted Answer

Ionic bonds involve the attraction between oppositely charged ions, while covalent bonds involve the sharing of electron pairs between atoms.

Question 4

A sample of methane ($$CH_4) is $$combusted in oxygen according to the reaction: $$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$. If you start with 16.0 g of methane, how many grams of water are produced? (Molar masses: CH_4$ = 16.0 g/$$mol, $$H_2O = 18.0 g/$$mol)

Accepted Answer

36.0 g

Question 5

Which of the following compounds is most likely to be ionic?

Accepted Answer

$$NaCl$$

Question 6

What is the correct name for the compound $$FeCl_3$$?

Accepted Answer

Iron(III) chloride

Question 7

Which of the following is the correct molecular formula for a compound with the empirical formula $$CH_2$$ and a molar mass of approximately 56 g/mol? (C = 12 g/mol, H = 1 g/mol)

Accepted Answer

$$C_4H_8$$

Question 8

Which of the following best describes the structure of an ionic solid such as sodium chloride?

Accepted Answer

A 3D lattice of alternating $$Na^+$$ and $$Cl^-$$ ions held together by electrostatic attraction.

Question 9

Which of the following is the correct name for $$H_2SO_4$$?

Accepted Answer

Sulfuric acid

Question 10

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula? (C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol)

Accepted Answer

$$CH_2O$$

Question 11

Which of the following is the correct name for $$NH_4$$^+$$?

Accepted Answer

Ammonium ion

Question 12

Which of the following is the correct formula for barium hydroxide?

Accepted Answer

$$Ba(OH)_2$$

Question 13

What is the molar mass of $$C_2H_6O ($$ethanol)? (C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol)

Accepted Answer

46.0 g/mol

Question 14

Which of the following is the correct name for $$NO_2$$?

Accepted Answer

Nitrogen dioxide

Question 15

How many molecules are present in 36.0 g of water ($$H_2O$$)? (Molar mass $$H_2O = 18.0 g/$$mol, Avogadro's number $$= 6.022 	imes 10$$^{23}$$ molecules/mol)

Accepted Answer

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

Question 16

Which of the following is the correct name for $$P_2O_5$$?

Accepted Answer

Diphosphorus pentoxide

Question 17

Which of the following is a correct statement about the naming of binary molecular compounds?

Accepted Answer

Prefixes are used to indicate the number of atoms of each element, and 'mono-' is never used for the first element.

Question 18

Which of the following is the correct formula for sodium phosphate?

Accepted Answer

$$Na_3PO_4$$

Question 19

A compound is found to contain 58.8% barium, 13.7% sulfur, and 27.5% oxygen by mass. What is its empirical formula? (Ba = 137 g/mol, S = 32.1 g/mol, O = 16.0 g/mol)

Accepted Answer

$$BaSO_4$$

Question 20

Which of the following is the correct name for $$HNO_2$$?

Accepted Answer

Nitrous acid

Chapter 3: Molecules and Compounds – Study Notes

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