Q: What is the correct formula for calculating the number of moles from a given mass and molar mass?

$$\text{Number of moles} = \frac{\text{Mass}}{\text{Molar mass}}$$

Q: Which of the following is the correct formula for calculating percent composition by mass?

$$\frac{\text{mass of element}}{\text{total mass of compound}} \times 100\%$$

Question 1

Which of the following best describes a compound?

Accepted Answer

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

Question 2

Which of the following is an example of a physical change?

Accepted Answer

Dissolving sugar in water

Question 3

Which law states that mass is neither created nor destroyed in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 4

A sample contains 0.025 kg of a substance. Express this mass in grams using the correct SI prefix.

Accepted Answer

$$25$$ grams

Question 5

Which scientist is credited with discovering the electron?

Accepted Answer

J.J. Thomson

Question 6

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons and electrons but different numbers of neutrons.

Question 7

Which of the following is a diatomic molecule?

Accepted Answer

O$$_2$$

Question 8

What is the correct formula for calculating the number of moles from a given mass and molar mass?

Accepted Answer

$$	ext{Number of moles} = \frac{	ext{Mass}}{	ext{Molar mass}}$$

Question 9

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two nonmetals.

Question 10

Which of the following is the correct representation for the isotope of carbon with 6 protons and 7 neutrons?

Accepted Answer

$$^{13}_{6}	ext{C}$$

Question 11

A student mixes two clear solutions and observes the formation of a precipitate. This is an example of:

Accepted Answer

A chemical change

Question 12

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

Accepted Answer

Atoms can be created or destroyed in chemical reactions.

Question 13

Which of the following is the correct scientific notation for 0.00056?

Accepted Answer

$$5.6 	imes 10$$^{-4}$$

Question 14

Which experiment led to the discovery of the nucleus in the atom?

Accepted Answer

Rutherford gold foil experiment

Question 15

Which of the following is a correct statement about the Law of Multiple Proportions?

Accepted Answer

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 16

Which of the following is the correct prefix for $$10^{-6}$$?

Accepted Answer

micro

Question 17

A molecule of water contains how many hydrogen atoms?

Accepted Answer

2

Question 18

Which of the following is a correct example of a homogeneous mixture?

Accepted Answer

Salt dissolved in water

Question 19

Which of the following is the correct formula for calculating percent composition by mass?

Accepted Answer

$$\frac{	ext{mass of element}}{	ext{total mass of compound}} 	imes 100\%$$

Question 20

Which of the following is a property of metals?

Accepted Answer

Good conductor of electricity

General Chemistry: Matter, Measurement, Atoms, and Elements

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