Question 1

Refer to the diagram with four circles containing blue cubes and red cylinders. Which circle best represents a homogeneous mixture?

Accepted Answer

c. Blue cubes and red cylinders evenly mixed

Question 2

According to the Law of Conservation of Mass, what will be the total mass of products if 10.0 g of hydrogen reacts completely with 80.0 g of oxygen to form water?

Accepted Answer

$$90.0\ \mathrm{g}$$

Question 3

Which of the following best describes the Law of Definite Proportions?

Accepted Answer

A compound always contains the same elements in the same proportion by mass.

Question 4

Given the following data for carbon monoxide (CO) and carbon dioxide (CO$$_2$$): $$	ext{CO: 12.01 g C, 16.00 g O}$$; $$	ext{CO}_2: 12.01 g C, 32.00 g O}. $$What is the ratio of oxygen in CO$$_2 to CO$$, and which law does this illustrate?

Accepted Answer

2:1; Law of Multiple Proportions

Question 5

A chemist decomposes three samples of a compound and finds the following mass ratios: Sample 1: 6 g C, 8 g O; Sample 2: 12 g C, 16 g O; Sample 3: 18 g C, 24 g O. What pattern do these results show?

Accepted Answer

The mass ratio of C to O is constant in all samples.

Question 6

Which statement is consistent with Dalton’s atomic theory as originally stated?

Accepted Answer

All cobalt atoms are identical.

Question 7

Which experiment led to the discovery of the electron?

Accepted Answer

J.J. Thomson's cathode ray experiment

Question 8

In Rutherford’s gold foil experiment, what observation led to the conclusion that the atom has a small, dense nucleus?

Accepted Answer

A few alpha particles were deflected at large angles.

Question 9

A chemist measures the charges on oil drops as $$-4.8 	imes 10$$^{-9}$$\ z$$, $$-9.6 	imes 10$$^{-9}$$\ z$$, $$-6.4 	imes 10$$^{-9}$$\ z$$, and $$-12.8 	imes 10$$^{-9}$$\ z. $$What is the charge of a single electron in zorgs ($$z$$)?

Accepted Answer

$$-3.2 	imes 10$$^{-9}$$\ z$$

Question 10

Which of the following statements about subatomic particles is FALSE?

Accepted Answer

Some atoms don’t have any protons.

Question 11

Which isotope is represented by the symbol $$^{14}_{7}\mathrm{N}$$?

Accepted Answer

Nitrogen with 7 protons and 7 neutrons

Question 12

A neutral atom of $$^{208}_{82}\mathrm{Pb}$$ contains how many protons and neutrons?

Accepted Answer

82 protons, 126 neutrons

Question 13

Which of the following ions has 34 electrons?

Accepted Answer

$$\mathrm{Cu}^{2+}$$

Question 14

Gallium has two naturally occurring isotopes: Ga-69 (60.108%) and Ga-71 (39.892%). What is the atomic mass of gallium?

Accepted Answer

$$69.723\ \mathrm{amu}$$

Question 15

Why does the mass spectrum of chlorine not show a peak at its atomic mass of $$35.45\ \mathrm{amu}$$?

Accepted Answer

Chlorine exists as two isotopes, and $$35.45\ \mathrm{amu} is $$the weighted average.

Question 16

How many sulfur atoms are present in $$5.52\ \mathrm{mol} of $$sulfur?

Accepted Answer

$$3.33 	imes 10$$^{24}$$

Question 17

A 7.83-g sample of HCN contains 0.290 g of H and 4.06 g of N. What is the mass of carbon in a 3.37-g sample of HCN?

Accepted Answer

$$1.48\ \mathrm{g}$$

Question 18

If you stacked Avogadro’s number ($$6.022 	imes 10$$^{23}$$) of pennies, each 1.0 mm thick, how far would the stack extend?

Accepted Answer

$$6.022 	imes 10$$^{20}$$\ \mathrm{km}$$

Question 19

Which of the following best distinguishes a scientific law from a scientific theory?

Accepted Answer

A law describes what happens; a theory explains why it happens.

Classification of Pure Substances and Mixtures Using Particle Diagrams

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