Q: Which of the following correctly expresses the relationship for calculating the number of moles from mass and molar mass?

$n = \frac{\text{mass}}{\text{molar mass}}$

Question 1

A sample of seawater is separated into its components by first filtering out sand and then boiling off the water to leave behind salt. Which separation techniques are being used in this process?

Accepted Answer

Filtration followed by distillation

Question 2

Which of the following statements best distinguishes between precision and accuracy in scientific measurements?

Accepted Answer

Precision refers to how close repeated measurements are to each other, while accuracy refers to how close a measurement is to the true value.

Question 3

A student measures the mass of a sample three times and obtains values of 2.51 g, 2.50 g, and 2.52 g. The true mass is 2.80 g. Which statement best describes the student's measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 4

Which of the following is a chemical change?

Accepted Answer

Iron rusting in moist air

Question 5

Which law is demonstrated when 12.0 g of carbon reacts completely with 32.0 g of oxygen to form 44.0 g of carbon dioxide?

Accepted Answer

Law of Conservation of Mass

Question 6

Which experiment provided evidence for the existence of the nucleus in the atom?

Accepted Answer

Rutherford's gold foil experiment

Question 7

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many protons, neutrons, and electrons does it have?

Accepted Answer

12 protons, 12 neutrons, 12 electrons

Question 8

Which of the following correctly expresses the relationship for calculating the number of moles from mass and molar mass?

Accepted Answer

$n = \frac{	ext{mass}}{	ext{molar mass}}$

Question 9

A compound contains 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 10

Which of the following is the correct balanced equation for the combustion of propane ($\mathrm{C_3H_8}$) in oxygen?

Accepted Answer

$\mathrm{C_3H_8} + 5\mathrm{O_2} \rightarrow 3\mathrm{CO_2} + 4\mathrm{H_2O}$

Question 11

A sample contains 0.50 mol of $\mathrm{NaCl}$. How many formula units of $\mathrm{NaCl}$ are present in the sample? ($N_A = 6.022 	imes 10^{23}\ 	ext{mol}^{-1}$)

Accepted Answer

$3.01 	imes 10^{23}$

Question 12

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 13

A 10.0 g sample of calcium carbonate ($\mathrm{CaCO_3}$) is decomposed by heating. How many grams of carbon dioxide ($\mathrm{CO_2}$) are produced? (Molar masses: $\mathrm{CaCO_3}$ = 100 g/mol, $\mathrm{CO_2}$ = 44 g/mol)

Accepted Answer

4.4 g

Question 14

Which of the following is a correct statement of 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 15

Which of the following ions is isoelectronic with neon ($\mathrm{Ne}$)?

Accepted Answer

$\mathrm{F^-}$

Question 16

A student is asked to prepare 250.0 mL of a 0.100 M $\mathrm{NaCl}$ solution. How many grams of $\mathrm{NaCl}$ are required? (Molar mass of $\mathrm{NaCl}$ = 58.44 g/mol)

Accepted Answer

1.46 g

Question 17

Which of the following is the correct name for $\mathrm{Fe_2O_3}$?

Accepted Answer

Iron(III) oxide

Question 18

Which of the following is a molecular compound?

Accepted Answer

$\mathrm{CO_2}$

Question 19

Which of the following is the correct formula for the compound formed between aluminum and sulfate?

Accepted Answer

$\mathrm{Al_2(SO_4)_3}$

Question 20

A reaction has a theoretical yield of 5.00 g and an actual yield of 4.20 g. What is the percent yield?

Accepted Answer

$84\%$

General Chemistry I: Study Guide for Chapters 1–4

Study Guide - Practice Questions

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