Question 1

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more elements chemically combined in a fixed ratio.

Question 2

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

Accepted Answer

Elements are arranged by increasing atomic number.

Question 3

A sample of a metal has a mass of $$ 45.0 \ \mathrm{g} $$ and a volume of $$ 15.0 \ \mathrm{cm}^3 . $$What is its density?

Accepted Answer

$$ 3.00 \ \mathrm{g/cm}^3 $$

Question 4

Which of the following is an example of an ionic bond?

Accepted Answer

The bond in $$ \mathrm{NaCl} $$

Question 5

Which SI unit would you use to measure the amount of a substance in a chemical reaction?

Accepted Answer

Mole

Question 6

A student measures the length of a metal rod as $$ 12.30 \ \mathrm{cm} . $$How many significant figures are in this measurement?

Accepted Answer

4

Question 7

Which of the following best explains why water ($$ \mathrm{H}_2O ) is $$considered a compound and not an element?

Accepted Answer

It can be separated into hydrogen and oxygen by chemical means.

Question 8

Which of the following statements about atoms is correct?

Accepted Answer

Protons and neutrons are found in the nucleus.

Question 9

A chemist needs to prepare $$ 250 \ \mathrm{mL}  of a $$solution. Which SI unit should be used to record the volume?

Accepted Answer

Liter

Question 10

Which of the following is a property of a pure substance?

Accepted Answer

It has a fixed composition.

Question 11

A student mixes two clear liquids and observes the formation of a solid. What type of change has most likely occurred?

Accepted Answer

A chemical change, because a new substance (solid) has formed.

Question 12

Which of the following best describes the difference between a solid and a gas?

Accepted Answer

A solid has a definite shape and volume, while a gas has neither.

Question 13

Which of the following is the correct formula for calculating density?

Accepted Answer

$$ d = \frac{m}{V} $$

Question 14

A sample of carbon dioxide ($$ \mathrm{CO}_2 ) $$gas is compressed from $$ 2.0 \ \mathrm{L}  to$$ $$ 1.0 \ \mathrm{L}  at $$constant temperature. Which property of the gas changes?

Accepted Answer

Its density increases.

Question 15

Which of the following is an example of a covalent bond?

Accepted Answer

The bond in $$ \mathrm{CO}_2 $$

Question 16

A hospital stores oxygen gas in a tank at $$ 300 \ \mathrm{K} . $$Which SI unit is used to measure this temperature?

Accepted Answer

Kelvin

Question 17

Which of the following best explains why significant figures are important in scientific measurements?

Accepted Answer

They express the precision of a measurement.

Question 18

A student is asked to identify an unknown substance. She finds it has a constant boiling point and a fixed composition. What can she conclude?

Accepted Answer

It is a pure substance.

Question 19

Which of the following best describes the difference between an element and a compound?

Accepted Answer

An element contains only one type of atom, while a compound contains two or more elements chemically combined.

Question 20

A laboratory technician needs to prepare a solution by dissolving $$ 10.0 \ \mathrm{g}  of $$salt in $$ 100.0 \ \mathrm{mL}  of $$water. If the final volume of the solution is $$ 105.0 \ \mathrm{mL} $$, what is the density of the solution?

Accepted Answer

$$ 0.095 \ \mathrm{g/mL} $$

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