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

Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with a uniform composition throughout, such as saltwater.

Question 2

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

Accepted Answer

Burning wood in a campfire.

Question 3

A student measures the mass of a sample three times and gets values very close to each other, but far from the true value. This is an example of:

Accepted Answer

Low accuracy, high precision

Question 4

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

Accepted Answer

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

Question 5

Convert 25.0°C to Kelvin.

Accepted Answer

$$K = 25.0 + 273.15 = 298.15\ K$$

Question 6

Which of the following statements about Dalton’s atomic theory is still considered true today?

Accepted Answer

Atoms of different elements combine in simple whole-number ratios to form compounds.

Question 7

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of CO_2$. How many moles of CO_2$ are present?

Accepted Answer

$$0.50$$ mol

Question 8

Which of the following ions is isoelectronic with Ne?

Accepted Answer

Na$$^+$$

Question 9

What is the empirical formula for a compound containing 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

CH$$_2O$$

Question 10

Which of the following best describes the trend in atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increasing effective nuclear charge.

Question 11

Which of the following molecules has a trigonal planar geometry according to VSEPR theory?

Accepted Answer

BCl$$_3$$

Question 12

How many significant figures are in the measurement 0.00420 g?

Accepted Answer

3

Question 13

Which of the following compounds is an ionic compound?

Accepted Answer

NaCl

Question 14

Which of the following is the correct electron configuration for a ground-state magnesium atom (Z=12)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$

Question 15

Which of the following is a property of metals?

Accepted Answer

Malleability

Question 16

Which of the following statements about sigma ($$\sigma) $$and pi ($$\pi) $$bonds is correct?

Accepted Answer

A triple bond consists of one sigma and two pi bonds.

Question 17

What is the molecular geometry of NH$$_3$$ according to VSEPR theory?

Accepted Answer

Trigonal pyramidal

Question 18

Which of the following is the correct formula for calculating percent composition by mass of an element in a compound?

Accepted Answer

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

Question 19

Which of the following best explains why the ionization energy increases across a period?

Accepted Answer

The effective nuclear charge increases, holding electrons more tightly.

Question 20

Which of the following is an example of a resonance structure?

Accepted Answer

O$$_3$$

Matter and Measurement: Foundations of General Chemistry

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