Q: A sample of water is heated from 25°C to 75°C. If the mass of water is 100 g and the specific heat is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, how much heat is absorbed?

$$q = 100\ \mathrm{g} \times 4.18\ \mathrm{J/g\cdot ^\circ C} \times (75 - 25)\ ^\circ C = 20,900\ \mathrm{J}$$

Q: A solution contains 5.0 g of NaCl in 100 mL of water. What is the percent by mass of NaCl in the solution?

$$\frac{5.0\ \mathrm{g}}{105.0\ \mathrm{g}} \times 100\% = 4.8\%$$

Question 1

Which of the following statements best describes a chemical property of copper?

Accepted Answer

Copper reacts with oxygen to form copper oxide.

Question 2

A student measures the mass of a sample as 12.30 g and its volume as 4.10 mL. What is the density of the sample, expressed in significant figures?

Accepted Answer

$$\frac{12.30\ \mathrm{g}}{4.10\ \mathrm{mL}} = 3.00\ \mathrm{g/mL}$$

Question 3

Which of the following is a mixture?

Accepted Answer

Air

Question 4

Which of the following best describes an endothermic reaction?

Accepted Answer

A reaction that absorbs heat from the surroundings.

Question 5

A sample of water is heated from 25°C to 75°C. If the mass of water is 100 g and the specific heat is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, how much heat is absorbed?

Accepted Answer

$$q = 100\ \mathrm{g} 	imes 4.18\ \mathrm{J/g\cdot ^\circ C} 	imes (75 - 25)\ ^\circ C = 20,900\ \mathrm{J}$$

Question 6

Which of the following elements is a noble gas?

Accepted Answer

Neon (Ne)

Question 7

What is the correct electron configuration for Argon (atomic number 18)?

Accepted Answer

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

Question 8

Which of the following ions is formed when magnesium reacts with chlorine?

Accepted Answer

Mg$$^{2+}$$ and Cl$$^{-}$$

Question 9

Which of the following compounds is ionic?

Accepted Answer

NaCl

Question 10

What is the molar mass of Ca(OH)$$_2$$?

Accepted Answer

$$74.10\ \mathrm{g/mol}$$

Question 11

Which statement about isotopes is correct?

Accepted Answer

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

Question 12

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their outer shell.

Question 13

Which of the following molecules is polar?

Accepted Answer

H$$_2O$$

Question 14

A solution contains 5.0 g of NaCl in 100 mL of water. What is the percent by mass of NaCl in the solution?

Accepted Answer

$$\frac{5.0\ \mathrm{g}}{105.0\ \mathrm{g}} 	imes 100\% = 4.8\%$$

Question 15

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have loosely held valence electrons that can move freely.

Question 16

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

Accepted Answer

Al$$_2(SO$_4$$)$$_3$$

Question 17

Which of the following statements about covalent bonds is true?

Accepted Answer

Covalent bonds involve the sharing of electrons between atoms.

Question 18

Which of the following is the correct Lewis structure for ammonia (NH$$_3$$)?

Accepted Answer

N with three single bonds to H and one lone pair on N

Question 19

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

Accepted Answer

A physical change alters the appearance but not the composition; a chemical change alters the composition.

Introduction to Chemistry: Core Concepts and Study Guide

Guida di studio - Domande di pratica

Study guide - Flashcard