Q: Calculate the atomic mass of chlorine given the following data: $$75.77\%$$ chlorine-35 (mass $$34.97$$ amu) and $$24.23\%$$ chlorine-37 (mass $$36.97$$ amu).

$$(0.7577 \times 34.97) + (0.2423 \times 36.97) = 35.45$$ amu

Q: How many atoms are present in $$3.5$$ mol of helium?

$$3.5 \times 6.022 \times 10$$^{23}$$ = 2.11 \times 10$$^{24}$$ atoms

Question 1

Which statement best describes the Law of Conservation of Mass as formulated by Antoine Lavoisier?

Accepted Answer

In a chemical reaction, the total mass of substances before and after the reaction remains unchanged.

Question 2

A sample of isooctane is analyzed and found to have a carbon-to-hydrogen mass ratio of 5.33:1. What law does this observation support?

Accepted Answer

Law of Constant Composition

Question 3

Which experiment provided evidence that atoms contain a small, dense, positively charged nucleus?

Accepted Answer

Rutherford’s gold foil experiment

Question 4

Which of the following is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms are composed of protons, neutrons, and electrons.

Question 5

A neutral atom of aluminum has an atomic number of 13. How many electrons does it have?

Accepted Answer

$$13$$

Question 6

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 7

Calculate the atomic mass of chlorine given the following data: $$75.77\%$$ chlorine-35 (mass $$34.97$$ amu) and $$24.23\%$$ chlorine-37 (mass $$36.97$$ amu).

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45$$ amu

Question 8

Which group on the periodic table contains the noble gases?

Accepted Answer

Group 8A

Question 9

A lithium atom loses one electron during a chemical reaction. What is the resulting ion and its charge?

Accepted Answer

$$\mathrm{Li}^+$$, +1$

Question 10

How many atoms are present in $$3.5$$ mol of helium?

Accepted Answer

$$3.5 	imes 6.022 	imes 10$$^{23}$$ = 2.11 	imes 10$$^{24}$$ atoms

Question 11

Which of the following best explains why the mass of a pebble, if each atom were the size of the pebble, would be larger than Mount Everest?

Accepted Answer

Atoms are extremely small and numerous in even a tiny sample of matter.

Question 12

Which subatomic particle was discovered by J.J. Thomson using the cathode ray tube experiment?

Accepted Answer

Electron

Question 13

What is the molar mass of carbon monoxide (CO)? (Atomic masses: C = 12.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$12.01 + 16.00 = 28.01 g/$$mol

Question 14

Which of the following is a correct symbol for an isotope of neon with 10 protons and 12 neutrons?

Accepted Answer

$$^{22}_{10}\mathrm{Ne}$$

Question 15

A fluoride ion ($$\mathrm{F}^-) $$has 9 protons and 10 electrons. What is its net charge?

Accepted Answer

$$-1$$

Question 16

Which property is shared by all isotopes of a given element?

Accepted Answer

Number of protons

Question 17

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

Accepted Answer

No charge, mass nearly equal to a proton

Question 18

Which group on the periodic table contains the alkali metals?

Accepted Answer

Group 1A

Question 19

How many moles of carbon are present in a $$0.58 g $$diamond? (Atomic mass of C = $$12.01 g/$$mol)

Accepted Answer

$$0.58 \div 12.01 = 0.048$$ mol$

Question 20

Which of the following best explains why atoms are electrically neutral?

Accepted Answer

The number of protons equals the number of electrons.

Atoms and Elements: Foundations of Matter and Atomic Theory

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