Q: Which formula is used to calculate the density of a substance?

$$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$$

Q: Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

$$\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}}$$

Question 1

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

Accepted Answer

An ionic bond involves the transfer of electrons from one atom to another, while a covalent bond involves the sharing of electrons between atoms.

Question 2

A student needs to convert 250 milliliters (mL) of water to liters (L). Which equation should they use, and what is the correct answer?

Accepted Answer

Use $$250 \div 1000 = 0.25 L$$; the answer is 0.25 L.

Question 3

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 4

A chemical reaction releases 150 kJ of energy. Which term best describes this reaction?

Accepted Answer

Exothermic

Question 5

Which of the following is the correct balanced equation for the combustion of methane ($$CH_4) in $$oxygen?

Accepted Answer

$$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$

Question 6

A sample of gas at 1.0 atm and 273 K occupies 22.4 L. If the pressure is doubled and the temperature remains constant, what will be the new volume?

Accepted Answer

11.2 L

Question 7

Which of the following is NOT a property of acids?

Accepted Answer

They feel slippery to the touch.

Question 8

Which formula is used to calculate the density of a substance?

Accepted Answer

$$	ext{Density} = \frac{	ext{Mass}}{	ext{Volume}}$$

Question 9

Which statement best explains why water is a polar molecule?

Accepted Answer

Water has a bent shape and unequal sharing of electrons between hydrogen and oxygen.

Question 10

A solution is prepared by dissolving 5.0 g of NaCl in enough water to make 250 mL of solution. What is the molarity of the solution? ($$M_{NaCl} = 58.44 g/$$mol)

Accepted Answer

$$0.20 M$$

Question 11

Which of the following best describes a buffer solution?

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added.

Question 12

Which law states that the volume of a gas is directly proportional to its temperature at constant pressure?

Accepted Answer

Charles's Law

Question 13

Which of the following is the correct electron configuration for a neutral oxygen atom?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^4$$

Question 14

Which of the following is a physical change?

Accepted Answer

Melting ice

Question 15

A student mixes 50 mL of 1.0 M HCl with 50 mL of 1.0 M NaOH. What is the expected pH of the resulting solution?

Accepted Answer

pH = 7

Question 16

Which of the following best describes the process of diffusion?

Accepted Answer

Movement of particles from an area of high concentration to low concentration.

Question 17

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$$	ext{Moles} = \frac{	ext{Mass}}{	ext{Molar Mass}}$$

Question 18

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

Accepted Answer

Elements in the same group have similar chemical properties.

Question 19

A compound contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$CH_2O$$

Question 20

Which of the following best explains why salt (NaCl) dissolves in water?

Accepted Answer

The positive and negative ions in NaCl are attracted to the partial charges on water molecules.

Introduction to Chemistry: Course Overview and Key Concepts

Guida di studio - Domande di pratica

Study guide - Flashcard