what is the ph of acids

HESI A2

Chemistry HESI A2 Practice Test

1. What is the pH of acids?

A. 7.5
B. < 7
C. > 7
D. 7

Correct answer: B

Rationale: The correct answer is B: < 7. Acids have a pH lower than 7, indicating higher acidity. A pH below 7 signifies an acidic solution, with lower values indicating stronger acids. Choice A (7.5) is incorrect as it is greater than 7, which is alkaline. Choice C (> 7) is incorrect as values greater than 7 represent alkaline/basic solutions. Choice D (7) is incorrect because a pH of 7 is neutral, not acidic.

2. Which compound contains a polar covalent bond?

A. O
B. F
C. Br
D. H₂O

Correct answer: D

Rationale: The compound 'H₂O' (water) contains a polar covalent bond. In a water molecule, the oxygen atom is more electronegative than the hydrogen atoms. As a result, the electrons in the O-H bonds are unevenly shared, leading to a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. This unequal sharing of electrons creates a polar covalent bond in water. Choices A, B, and C are incorrect because they represent individual elements, not compounds, and do not involve the concept of polar covalent bonds.

3. To the nearest whole number, what is the mass of one mole of sodium chloride?

A. 36 g/mol
B. 43 g/mol
C. 58 g/mol
D. 72 g/mol

Correct answer: C

Rationale: The molar mass of sodium chloride (NaCl) is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl). The atomic mass of sodium is approximately 23 g/mol and chlorine is approximately 35.5 g/mol. Adding these two atomic masses gives us a molar mass of approximately 58 g/mol for sodium chloride (NaCl). Therefore, the correct answer is C, 58 g/mol. Choice A (36 g/mol) is incorrect as it does not account for the individual atomic masses of sodium and chlorine. Choice B (43 g/mol) and choice D (72 g/mol) are also incorrect as they do not reflect the accurate molar mass of sodium chloride.

4. What does the term amphoteric mean?

A. A substance that only acts as a base
B. A substance that can act as both a base and an acid
C. A substance that only acts as an acid
D. A substance that acts as neither a base nor an acid

Correct answer: B

Rationale: The term 'amphoteric' refers to substances that have the ability to act as both acids and bases depending on the surrounding conditions. This dual nature allows amphoteric substances to donate or accept protons, making them versatile in various chemical reactions. Choice A is incorrect because amphoteric substances can also act as acids. Choice C is incorrect as amphoteric substances can also act as bases. Choice D is incorrect as amphoteric substances can act as either a base or an acid.

5. What is the term used when an atom gains one or more electrons?

A. Cation
B. Anion
C. Isotope
D. Electron

Correct answer: B

Rationale: When an atom gains electrons, it becomes negatively charged and is called an anion. An anion is formed when an atom gains one or more electrons, leading to an excess of negative charge. Choice A, 'Cation,' is incorrect because a cation is formed when an atom loses electrons, resulting in a positively charged ion. Choice C, 'Isotope,' refers to atoms of the same element with different numbers of neutrons and is not related to gaining electrons. Choice D, 'Electron,' is the particle that an atom gains to become an anion, not the term for the atom itself after gaining electrons.