Question 1

Which postulate of Dalton’s atomic theory explains why the mass of matter remains constant during a chemical reaction?

Accepted Answer

Atoms are neither created nor destroyed during a chemical change, but instead rearrange to yield different types of matter.

Question 2

A sample of copper(II) oxide contains copper and oxygen atoms in a 1:1 ratio. Which law does this observation best illustrate?

Accepted Answer

Law of definite proportions

Question 3

In the cathode ray tube experiment, what evidence indicated that the particles in the ray were negatively charged?

Accepted Answer

The beam was always deflected toward the positive plate and away from the negative plate.

Question 4

Millikan’s oil drop experiment determined the charge of a single electron. If the charge on an oil drop was always a multiple of $$1.6 	imes 10$$^{-19}$$\ \mathrm{C}$$, what does this imply about electric charge?

Accepted Answer

Electric charge is quantized.

Question 5

Rutherford’s gold foil experiment led to which major conclusion about atomic structure?

Accepted Answer

Atoms have a small, dense, positively charged nucleus.

Question 6

A neutral atom of sodium (Na) has 11 protons and 11 electrons. What is the charge and electron count of a sodium ion (Na$$^+) $$formed when it reacts with chlorine?

Accepted Answer

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

Question 7

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 8

Calculate the average atomic mass of boron given the following isotopic abundances: $$19.9\%$$ $$^{10}\mathrm{B} ($$mass $$= 10.0129$$ amu) and $$80.1\%$$ $$^{11}\mathrm{B} ($$mass $$= 11.0093$$ amu).

Accepted Answer

$$10.81$$ amu

Question 9

Which of the following is the correct empirical formula for acetic acid, $$\mathrm{C}_2\mathrm{H}_4\mathrm{O}_2$$?

Accepted Answer

$$\mathrm{CH}_2\mathrm{O}$$

Question 10

Which of the following elements is a metalloid based on its position in the periodic table?

Accepted Answer

Silicon (Si)

Question 11

Which of the following compounds is an example of an ionic compound containing a polyatomic ion?

Accepted Answer

$$\mathrm{CaSO}_4$$

Question 12

What is the correct name for the compound $$\mathrm{FeCl}_3$$?

Accepted Answer

Iron(III) chloride

Question 13

Which of the following is the correct formula for aluminum oxide, given that aluminum forms $$\mathrm{Al}^{3+}$$ ions and oxygen forms $$\mathrm{O}^{2-}$$ ions?

Accepted Answer

$$\mathrm{Al}_2\mathrm{O}_3$$

Question 14

Which of the following best describes the difference between a molecular formula 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.

Question 15

Which of the following is the correct name for $$\mathrm{N}_2\mathrm{O}_4$$?

Accepted Answer

Dinitrogen tetroxide

Question 16

Which of the following acids is correctly named as 'sulfuric acid'?

Accepted Answer

$$\mathrm{H}_2\mathrm{SO}_4$$

Question 17

A compound contains only potassium and bromine. What is the correct formula and name for this compound?

Accepted Answer

$$\mathrm{KBr}$$, potassium bromide

Question 18

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

Accepted Answer

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

Question 19

Which of the following is a property of ionic compounds?

Accepted Answer

They conduct electricity when molten.

Question 20

Which of the following is the correct name for $$\mathrm{P}_4\mathrm{O}_{10}$$?

Accepted Answer

Tetraphosphorus decoxide

Atoms, Elements, and the Foundations of Modern Atomic Theory

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