Q: A student needs to convert $$5.0 \\ \mathrm{cm} to$$ $$\mathrm{mm}. $$Which of the following is the correct answer and conversion factor used?

$$5.0 \\ \mathrm{cm} \times \frac{10 \\ \mathrm{mm}}{1 \\ \mathrm{cm}} = 50 \\ \mathrm{mm}$$

Q: A sample of glucose ($$\mathrm{C_6H_{12}O_6$}) $$contains $$1.20 \\ \times 10$$^{24}$$ molecules. How many moles of glucose are present?

$$1.99 \\ \times 10$$^{-1}$$ \\ \mathrm{mol}$$

Q: Which of the following is the correct formula for calculating the average atomic mass of an element with two isotopes?

$$\text{Average atomic mass} = (\text{fraction}_1 \times \text{mass}_1) + (\text{fraction}_2 \times \text{mass}_2)$$

Question 1

Which of the following best describes a physical change?

Accepted Answer

Dissolving table salt in water

Question 2

Which statement about atoms and molecules is correct?

Accepted Answer

Atoms are the smallest units of an element that retain the properties of that element.

Question 3

A student measures the mass of a sample as 12.30 g and its volume as 4.1 mL. What is the density of the sample, reported with the correct number of significant figures?

Accepted Answer

$$3.0 \ \mathrm{g/mL}$$

Question 4

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

Accepted Answer

Ability of iron to rust

Question 5

Which law states that a chemical compound always contains the same proportion of elements by mass?

Accepted Answer

Law of Definite Proportions

Question 6

A sample contains $$2.50 \ \mathrm{mol} of$$ $$\mathrm{NaCl}. $$How many formula units of $$\mathrm{NaCl}$$ are present in the sample? ($$N_A = 6.022 \ 	imes 10$$^{23}$$ \ \mathrm{mol}^{-1})$$

Accepted Answer

$$1.51 \ 	imes 10$$^{24}$$

Question 7

Which of the following best explains why atomic masses listed in the periodic table are not whole numbers?

Accepted Answer

Because atomic masses are averages of the masses of all naturally occurring isotopes

Question 8

Which of the following is the correct formula to convert temperature from Celsius to Kelvin?

Accepted Answer

$$K = ^\circ C + 273.15$$

Question 9

A student needs to convert $$5.0 \ \mathrm{cm} to$$ $$\mathrm{mm}. $$Which of the following is the correct answer and conversion factor used?

Accepted Answer

$$5.0 \ \mathrm{cm} 	imes \frac{10 \ \mathrm{mm}}{1 \ \mathrm{cm}} = 50 \ \mathrm{mm}$$

Question 10

Which of the following statements about Dalton’s atomic theory is NOT correct based on modern understanding?

Accepted Answer

Atoms of a given element are identical in mass and properties.

Question 11

A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 12

Which of the following best describes the difference between accuracy and precision?

Accepted Answer

Accuracy refers to how close measurements are to the true value, while precision refers to how close measurements are to each other.

Question 13

Which of the following is the correct number of significant figures in the measurement $$0.00450$$?

Accepted Answer

3

Question 14

A sample of glucose ($$\mathrm{C_6H_{12}O_6$}) $$contains $$1.20 \ 	imes 10$$^{24}$$ molecules. How many moles of glucose are present?

Accepted Answer

$$1.99 \ 	imes 10$$^{-1}$$ \ \mathrm{mol}$$

Question 15

Which of the following is the correct order of steps to convert mass of a compound to number of atoms of an element in the compound?

Accepted Answer

Mass $$\rightarrow$$ Moles $$\rightarrow$$ Molecules $$\rightarrow$$ Atoms

Question 16

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 17

Which of the following is the correct formula for calculating the average atomic mass of an element with two isotopes?

Accepted Answer

$$	ext{Average atomic mass} = (	ext{fraction}_1 	imes 	ext{mass}_1) + (	ext{fraction}_2 	imes 	ext{mass}_2)$$

Question 18

A student is asked to multiply $$2.34 (3 $$sig figs) by $$1.2 (2 $$sig figs). What is the correct answer with the proper number of significant figures?

Accepted Answer

$$2.8$$

Question 19

Which of the following best describes the main difference between a scientific theory and a scientific law?

Accepted Answer

A scientific theory explains why phenomena occur, while a scientific law describes what happens.

General Chemistry: Foundations, Atoms, and Elements – Study Guide

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