Question 1

Which statement best describes the law of definite proportions as formulated by Joseph Proust?

Accepted Answer

Different samples of the same compound always contain the constituent elements in the same proportion by mass.

Question 2

Which experiment led to the discovery that the atom is mostly empty space with a dense central nucleus?

Accepted Answer

Rutherford's gold foil experiment using alpha particles.

Question 3

Given the following data for chlorine isotopes: $$^{35}\mathrm{Cl} ($$mass = 35 amu, abundance = 77.4%) and $$^{37}\mathrm{Cl} ($$mass = 37 amu, abundance = 22.6%), what is the average atomic mass of chlorine?

Accepted Answer

$$35.452\ \mathrm{amu}$$

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 5

A neutral atom of sodium ($$\mathrm{Na}) $$has an atomic number of 11 and an atomic mass of approximately 23 amu. How many protons, neutrons, and electrons does it have?

Accepted Answer

11 protons, 12 neutrons, 11 electrons

Question 6

Which of the following is a homonuclear diatomic molecule?

Accepted Answer

$$\mathrm{O}_2$$

Question 7

Which group in the periodic table contains elements that are all unreactive under normal conditions?

Accepted Answer

Group 8A (Noble gases)

Question 8

Which of the following best explains why the mass number of an element is not always a whole number?

Accepted Answer

The element exists as a mixture of isotopes with different numbers of neutrons.

Question 9

Which of the following is the correct structural formula for water, considering hydrogen's bonding capacity?

Accepted Answer

H-O-H

Question 10

Which of the following ions has the greatest number of electrons?

Accepted Answer

$$\mathrm{F}^-$$

Question 11

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 12

Which of the following is a polyatomic molecule?

Accepted Answer

$$\mathrm{SO}_3$$

Question 13

Which of the following best describes the charge and mass of a neutron?

Accepted Answer

No charge, mass slightly greater than a proton

Question 14

Which of the following is the correct formula for diphosphorus pentoxide?

Accepted Answer

$$\mathrm{P}_2\mathrm{O}_5$$

Question 15

A sample of silver contains two isotopes: $$^{107}\mathrm{Ag} (106.90 $$amu) and $$^{109}\mathrm{Ag} (108.90 $$amu). If the average atomic mass is 107.87 amu, what is the natural abundance of $$^{107}\mathrm{Ag}$$?

Accepted Answer

51.5%

Question 16

Which of the following best describes the law of multiple proportions?

Accepted Answer

If two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 17

Which of the following is a heteronuclear diatomic molecule?

Accepted Answer

$$\mathrm{CO}$$

Question 18

Which element is a metalloid?

Accepted Answer

Silicon (Si)

Question 19

Which of the following statements about the plum-pudding model of the atom is correct?

Accepted Answer

It proposed that electrons are embedded in a sphere of uniform positive charge.

Question 20

Which of the following is the correct formula for ammonia?

Accepted Answer

$$\mathrm{NH}_3$$

chapter 2 lec 1

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