Q: Which of the following best describes Avogadro's number?

The number of atoms in one mole of a substance, $$6.022 \times 10$$^{23}$$.

Q: A naturally occurring element has two isotopes: $$^{35}\mathrm{Cl} (75.8$$% abundance, mass = 34.97 amu) and $$^{37}\mathrm{Cl} (24.2$$% abundance, mass = 36.97 amu). What is the average atomic mass of chlorine?

$$(0.758 \times 34.97) + (0.242 \times 36.97) = 35.45$$ amu

Q: A sample of magnesium contains $$1.20 \times 10$$^{24}$$ atoms. What is the mass of this sample? (Molar mass of Mg = 24.3 g/mol)

$$(1.20 \times 10$$^{24}$$ \div 6.022 \times 10$$^{23}$$) \times 24.3 = 48.4 g$$

Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout, such as salt dissolved in water.

Question 2

Which of the following statements is NOT one of Dalton's postulates of atomic theory?

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 3

J.J. Thomson's cathode ray tube experiment provided evidence for which subatomic particle?

Accepted Answer

Electron

Question 4

Which of the following correctly defines the atomic mass unit (amu)?

Accepted Answer

The mass of a single proton or neutron, approximately $$1.66 	imes 10$$^{-24}$$ grams.

Question 5

An isotope of carbon has 6 protons and 8 neutrons. What is its chemical symbol with mass number?

Accepted Answer

$$^{14}\mathrm{C}$$

Question 6

Which of the following best describes Avogadro's number?

Accepted Answer

The number of atoms in one mole of a substance, $$6.022 	imes 10$$^{23}$$.

Question 7

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of water. How many moles of water are present?

Accepted Answer

$$0.5$$ moles

Question 8

Which law states that a chemical compound always contains the same proportion of elements by mass?

Accepted Answer

Law of Definite Proportions

Question 9

A naturally occurring element has two isotopes: $$^{35}\mathrm{Cl} (75.8$$% abundance, mass = 34.97 amu) and $$^{37}\mathrm{Cl} (24.2$$% abundance, mass = 36.97 amu). What is the average atomic mass of chlorine?

Accepted Answer

$$(0.758 	imes 34.97) + (0.242 	imes 36.97) = 35.45$$ amu

Question 10

Which of the following is a correct statement about ions?

Accepted Answer

An anion is formed when an atom gains one or more electrons.

Question 11

Which experiment provided evidence for the existence of the nucleus in the atom?

Accepted Answer

Rutherford's gold foil experiment

Question 12

A sample of magnesium contains $$1.20 	imes 10$$^{24}$$ atoms. What is the mass of this sample? (Molar mass of Mg = 24.3 g/mol)

Accepted Answer

$$(1.20 	imes 10$$^{24}$$ \div 6.022 	imes 10$$^{23}$$) 	imes 24.3 = 48.4 g$$

Question 13

Which of the following is a pure substance?

Accepted Answer

Oxygen gas ($$\mathrm{O}_2)$$

Question 14

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

Accepted Answer

An element consists of only one type of atom, while a compound consists of two or more different elements chemically combined.

Question 15

Which of the following is the correct symbol for an ion with 17 protons and 18 electrons?

Accepted Answer

$$\mathrm{Cl}^-$$

Question 16

A mass spectrometer is used to determine the relative abundance of isotopes. Which property of the ions allows them to be separated in the mass spectrometer?

Accepted Answer

Their mass-to-charge ratio ($$m/z)$$

Question 17

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 18

Which of the following is the correct definition of radioactivity?

Accepted Answer

The spontaneous emission of particles or energy from an unstable atomic nucleus.

Question 19

If an atom has an atomic number of 15 and a mass number of 31, how many neutrons does it have?

Accepted Answer

$$31 - 15 = 16$$ neutrons

Question 20

Which of the following best describes a chemical symbol?

Accepted Answer

A one- or two-letter abbreviation for an element, such as $$\mathrm{Na}$$ for sodium.

General Chemistry - Chapter 1

Guida di studio - Domande di pratica

Study guide - Flashcard