to the nearest whole number what is the mass of one mole of water
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HESI A2

Chemistry HESI A2 Practice Test

1. To the nearest whole number, what is the mass of one mole of water?

Correct answer: B

Rationale: The molar mass of water (Hâ‚‚O) is calculated by adding the atomic masses of two hydrogen atoms (each with a molar mass of approximately 1 g/mol) and one oxygen atom (with a molar mass of approximately 16 g/mol). Therefore, the molar mass of water is approximately 18 g/mol, making choice B the correct answer. Choice A (16 g/mol) is incorrect because it represents the molar mass of oxygen, not water. Choices C (20 g/mol) and D (22 g/mol) are incorrect as they do not correspond to the molar mass of water.

2. What is 119 K in degrees Celsius?

Correct answer: B

Rationale: To convert Kelvin (K) to Celsius (°C), you subtract 273.15 from the Kelvin value. Therefore, 119 K - 273.15 = -154.15°C. The negative sign indicates that the temperature is below freezing. When rounded to the nearest whole number, -154.15°C is approximately -154°C. Choice A and Choice C are incorrect as they do not reflect the correct conversion from Kelvin to Celsius. Choice D is incorrect as it corresponds to the freezing point of water in Celsius, not the conversion of 119 K.

3. What are negatively charged ions called?

Correct answer: C

Rationale: Negatively charged ions are called anions. Anions gain electrons and carry a negative charge, which distinguishes them from cations that are positively charged and neutrons and protons that are subatomic particles found in the nucleus of an atom. Choice A, Neutrons, are neutral subatomic particles found in the nucleus of an atom, not negatively charged ions. Choice B, Protons, are positively charged subatomic particles found in the nucleus of an atom, not negatively charged ions. Choice D, Cations, are positively charged ions that lose electrons, which is opposite to the behavior of negatively charged ions.

4. In the periodic table, which group contains the alkali metals?

Correct answer: B

Rationale: The correct answer is Group 1. Alkali metals are found in Group 1 of the periodic table, which includes elements such as lithium, sodium, and potassium. These elements are known for their high reactivity and tendency to form alkaline solutions when they react with water. Therefore, Group 1 is specifically designated as the group containing alkali metals. Choice A (Group 7) is incorrect as Group 7 contains the halogens. Choice C (Group 2) is incorrect as Group 2 contains the alkaline earth metals. Choice D (Group 3) is incorrect as Group 3 contains the scandium group of elements.

5. Which of the following elements does not exist as a diatomic molecule?

Correct answer: A

Rationale: The correct answer is 'boron.' Diatomic molecules consist of two atoms of the same element bonded together. Boron is an exception and does not exist naturally as a diatomic molecule. On the other hand, fluorine, oxygen, and nitrogen commonly exist as diatomic molecules in their natural states. Fluorine, for example, exists as F2, oxygen exists as O2, and nitrogen exists as N2.

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