Q: Calculate the average atomic mass of an element with two isotopes: 70% $$^{63}\mathrm{Cu} ($$mass = 62.93 amu) and 30% $$^{65}\mathrm{Cu} ($$mass = 64.93 amu).

$$0.70 \times 62.93 + 0.30 \times 64.93 = 63.53$$ amu

Question 1

Which of the following statements is NOT a postulate of Dalton’s Atomic Theory?

Accepted Answer

Atoms are composed of protons, neutrons, and electrons.

Question 2

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

Accepted Answer

Rutherford’s gold foil experiment

Question 3

A neutral atom of $$^{32}\mathrm{P}$$ contains how many protons, neutrons, and electrons?

Accepted Answer

15 protons, 17 neutrons, 15 electrons

Question 4

Which law states that when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small, whole numbers?

Accepted Answer

Law of multiple proportions

Question 5

Which scientist is credited with discovering the charge-to-mass ratio of the electron using a cathode ray tube?

Accepted Answer

J.J. Thomson

Question 6

Calculate the average atomic mass of an element with two isotopes: 70% $$^{63}\mathrm{Cu} ($$mass = 62.93 amu) and 30% $$^{65}\mathrm{Cu} ($$mass = 64.93 amu).

Accepted Answer

$$0.70 	imes 62.93 + 0.30 	imes 64.93 = 63.53$$ amu

Question 7

Which group on the periodic table contains the halogens?

Accepted Answer

Group 17

Question 8

What is the empirical formula for the compound with the molecular formula $$\mathrm{C}_4\mathrm{H}_8\mathrm{O}_2$$?

Accepted Answer

$$\mathrm{C}_2\mathrm{H}_4\mathrm{O}$$

Question 9

Which of the following compounds is an acid?

Accepted Answer

$$\mathrm{H}_2\mathrm{SO}_4 (aq)$$

Question 10

Which of the following best describes the difference between a molecular and an empirical formula?

Accepted Answer

A molecular formula shows the actual number of atoms of each element in a molecule, while an empirical formula shows the simplest whole-number ratio of the elements.

Question 11

Which of the following ions is formed when a magnesium atom loses two electrons?

Accepted Answer

$$\mathrm{Mg}^{2+}$$

Question 12

Which of the following is the correct name for $$\mathrm{Fe(NO}_3)_2$$?

Accepted Answer

Iron(II) nitrate

Question 13

Which property is shared by all elements in Group 1 (alkali metals) of the periodic table?

Accepted Answer

They form $$+1$$ ions.

Question 14

Which of the following best explains why most of the mass of an atom is concentrated in the nucleus?

Accepted Answer

Protons and neutrons, which are much heavier than electrons, are located in the nucleus.

Question 15

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

Accepted Answer

$$\mathrm{Ba(OH)}_2$$

Question 16

A sample of a compound contains 40.0 g of carbon and 6.7 g of hydrogen. What is the empirical formula of the compound? (Atomic masses: C = 12, H = 1)

Accepted Answer

$$\mathrm{CH}_2$$

Question 17

Which of the following best describes the periodic law?

Accepted Answer

The properties of elements are periodic functions of their atomic numbers.

Question 18

Which of the following is the correct name for $$\mathrm{CO}_2$$?

Accepted Answer

Carbon dioxide

Question 19

Which of the following is a property of metals on the periodic table?

Accepted Answer

They are good conductors of electricity.

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