Q: How many molecules are present in $$0.0400 g of $$saccharin ($$\mathrm{C}_7\mathrm{H}_5\mathrm{NO}_3\mathrm{S}$$, molar mass $$183.18 g/$$mol)? Use Avogadro's number $$6.022 \times 10$$^{23}$$ mol$$^{-1}$$.

$$1.32 \times 10$$^{20}$$ molecules

Question 1

Which of the following statements best explains the law of conservation of matter as supported by Dalton's atomic theory?

Accepted Answer

Atoms are rearranged during a chemical reaction, but the total number of atoms remains constant.

Question 2

A compound contains 0.558 g of chlorine for every 1 g of copper. Another compound contains 1.116 g of chlorine for every 1 g of copper. What law does this data illustrate?

Accepted Answer

Law of multiple proportions

Question 3

Which experiment led to the discovery of the electron and what was the key observation?

Accepted Answer

Thomson's cathode ray tube experiment; the beam was deflected by electric and magnetic fields.

Question 4

Which subatomic particle has a mass of approximately $$1.0087$$ amu and no electric charge?

Accepted Answer

Neutron

Question 5

An atom of magnesium has 12 protons, 13 neutrons, and 10 electrons. What is its chemical symbol with charge and mass number?

Accepted Answer

$$^{25}_{12}\mathrm{Mg}^{2+}$$

Question 6

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 7

Calculate the average atomic mass of an element that has two isotopes: 20% $$^{10}\mathrm{X} (10.0 $$amu) and 80% $$^{11}\mathrm{X} (11.0 $$amu).

Accepted Answer

$$10.8$$ amu

Question 8

A neutral atom of sodium ($$Z=11) $$loses one electron. What is the resulting ion's charge and electron count?

Accepted Answer

Charge: $$1+$$, Electrons: $$10$$

Question 9

Which formula represents the simplest whole-number ratio of atoms in a compound?

Accepted Answer

Empirical formula

Question 10

How many molecules are present in $$0.0400 g of $$saccharin ($$\mathrm{C}_7\mathrm{H}_5\mathrm{NO}_3\mathrm{S}$$, molar mass $$183.18 g/$$mol)? Use Avogadro's number $$6.022 	imes 10$$^{23}$$ mol$$^{-1}$$.

Accepted Answer

$$1.32 	imes 10$$^{20}$$ molecules

Question 11

Which of the following elements exists naturally as a diatomic molecule?

Accepted Answer

Nitrogen

Question 12

A sample contains $$9.2 	imes 10$$^{-3}$$ mol of argon. What is the mass of argon in the sample? (Molar mass of Ar = 39.95$ g/mol)

Accepted Answer

$$0.037 g$$

Question 13

Which scientist's experiment provided evidence for a small, dense, positively charged nucleus at the center of the atom?

Accepted Answer

Ernest Rutherford

Question 14

What is the molar mass of vitamin C ($$\mathrm{C}_6\mathrm{H}_8\mathrm{O}_6$$)? (Atomic masses: C = $$12.01 g/$$mol, H = $$1.008 g/$$mol, O = $$16.00 g/$$mol)

Accepted Answer

$$176.12 g/$$mol

Question 15

Which of the following is a structural isomer of acetic acid ($$\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$$)?

Accepted Answer

Methyl formate

Question 16

If a neutral atom has 17 protons and 18 neutrons, what is its atomic number and mass number?

Accepted Answer

Atomic number: $$17$$, Mass number: $$35$$

Question 17

Which of the following best describes Avogadro's number?

Accepted Answer

The number of atoms in one mole of carbon-12

Question 18

A molecule of benzene has the molecular formula $$\mathrm{C}_6\mathrm{H}_6. $$What is its empirical formula?

Accepted Answer

$$\mathrm{CH}$$

Question 19

Which of the following statements is true about ions?

Accepted Answer

Anions are formed when atoms gain electrons.

Atoms, Molecules, and Ions: Foundations of Atomic Theory and Chemical Formulas

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