Question 1

Which of the following statements best describes the difference between a physical change and a chemical change?

Accepted Answer

A chemical change results in the formation of new substances, while a physical change does not alter the chemical identity.

Question 2

A student measures the mass of a sample as 12.34 g and its volume as 4.56 mL. What is the density of the sample, and which significant figures rule applies to the answer?

Accepted Answer

Density $$= \frac{12.34}{4.56} = 2.71\ \mathrm{g/mL}$$; answer should have 3 significant figures because volume has 3.

Question 3

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

Accepted Answer

Rutherford's gold foil experiment

Question 4

Which of the following is the correct electron configuration for a neutral atom of sodium ($$Z=11$$)?

Accepted Answer

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

Question 5

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$$CH_2O$$

Question 6

Which of the following best describes the difference between an ionic and a covalent compound?

Accepted Answer

Ionic compounds involve the transfer of electrons from a metal to a nonmetal, while covalent compounds involve the sharing of electrons between nonmetals.

Question 7

A student balances the following chemical equation: $$\mathrm{C}_2\mathrm{H}_6 + \mathrm{O}_2 \rightarrow \mathrm{CO}_2 + \mathrm{H}_2\mathrm{O}. $$What are the correct coefficients?

Accepted Answer

$$2, 7, 4, 6$$

Question 8

Which statement about isotopes is correct?

Accepted Answer

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

Question 9

Which of the following is the correct molar mass for calcium nitrate, $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

$$164\ \mathrm{g/mol}$$

Question 10

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

Accepted Answer

$$0.50\ \mathrm{mol}$$

Question 11

Which of the following is a decomposition reaction?

Accepted Answer

$$2\mathrm{KClO}_3 \rightarrow 2\mathrm{KCl} + 3\mathrm{O}_2$$

Question 12

Which of the following best explains why balanced chemical equations are necessary for stoichiometric calculations?

Accepted Answer

They reflect the law of conservation of mass, ensuring the same number of atoms of each element on both sides.

Question 13

A reaction has a theoretical yield of 10.0 g and an actual yield of 8.0 g. What is the percent yield?

Accepted Answer

$$80\%$$

Question 14

Which of the following elements is a metalloid?

Accepted Answer

Silicon ($$\mathrm{Si})$$

Question 15

Which of the following is the correct formula for aluminum sulfate?

Accepted Answer

$$\mathrm{Al}_2\mathrm{(SO_4$)_3}$$

Question 16

Which of the following is the correct balanced equation for the reaction of sodium with chlorine gas?

Accepted Answer

$$2\mathrm{Na} + \mathrm{Cl}_2 \rightarrow 2\mathrm{NaCl}$$

Question 17

Which of the following best describes the limiting reactant in a chemical reaction?

Accepted Answer

The reactant that determines the amount of product formed.

Question 18

Which of the following is the correct calculation for the number of atoms in 2.00 moles of helium?

Accepted Answer

$$2.00 	imes 6.022 	imes 10$$^{23}$$ = 1.20 	imes 10$$^{24}$$ atoms

Question 19

Which of the following is a correct statement about the periodic table?

Accepted Answer

Elements in the same group have the same number of valence electrons.

Study Guide: CHEM 134 Exam 1 (Chapters 1–4) – Matter, Atoms, Molecules, and Chemical Reactions

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