Q: A naturally occurring sample of chlorine contains 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). What is the atomic mass of chlorine?

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

Q: How many atoms are in 2.50 mol of aluminum?

$$2.50 \times 6.022 \times 10$$^{23}$$ = 1.51 \times 10$$^{24}$$ atoms

Q: If you have $$3.00 \times 10$$^{24}$$ atoms of copper, how many moles of copper do you have?

$$\frac{3.00 \times 10$$^{24}$$}{6.022 \times 10$$^{23}$$} = 4.98$$ mol

Question 1

Which statement best describes the difference between a scientific law and a scientific theory?

Accepted Answer

A law summarizes a series of related observations, while a theory gives the underlying reasons for them.

Question 2

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

Accepted Answer

Sweetened tea

Question 3

A sample of water decomposes to produce 16.0 g of oxygen and 2.0 g of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$\frac{16.0}{2.0} = 8.0$$

Question 4

Which experiment led to the discovery of the electron?

Accepted Answer

Thomson's cathode ray experiment

Question 5

What is the charge of a single electron as determined by Millikan's oil drop experiment?

Accepted Answer

$$1.60 	imes 10$$^{-19}$$ C

Question 6

Which statement about the atomic nucleus is correct according to Rutherford's nuclear model?

Accepted Answer

Most of the atom's mass and all of its positive charge are contained in a small core called the nucleus.

Question 7

An atom of neon has 10 protons and 12 neutrons. What is its mass number and how is it represented?

Accepted Answer

Mass number $$A = 22$$, represented as Ne-22

Question 8

Which of the following is NOT a subatomic particle found in atoms?

Accepted Answer

Photon

Question 9

A naturally occurring sample of chlorine contains 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). What is the atomic mass of chlorine?

Accepted Answer

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

Question 10

How many atoms are in 2.50 mol of aluminum?

Accepted Answer

$$2.50 	imes 6.022 	imes 10$$^{23}$$ = 1.51 	imes 10$$^{24}$$ atoms

Question 11

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more elements in fixed, definite proportions.

Question 12

What is the molar mass of carbon?

Accepted Answer

$$12.01 g/$$mol

Question 13

If you have $$3.00 	imes 10$$^{24}$$ atoms of copper, how many moles of copper do you have?

Accepted Answer

$$\frac{3.00 	imes 10$$^{24}$$}{6.022 	imes 10$$^{23}$$} = 4.98$$ mol

Question 14

Which of the following statements is true about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 15

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

Accepted Answer

Law of conservation of mass

Question 16

A sample contains two compounds of elements A and B. Compound 1 has 2 g of B per 1 g of A, and Compound 2 has 4 g of B per 1 g of A. What law does this illustrate?

Accepted Answer

Law of multiple proportions

Question 17

Which instrument allows scientists to image and manipulate individual atoms on a surface?

Accepted Answer

Scanning tunneling microscope (STM)

Question 18

What is the number of protons in the nucleus of an atom called?

Accepted Answer

Atomic number ($$Z)$$

Question 19

Which of the following is a cation?

Accepted Answer

Na$$^+$$

Atoms and the Classification of Matter: Foundations of General Chemistry

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