HESI A2 Chemistry

Questions 33

HESI A2

HESI A2 Test Bank

HESI A2 Chemistry Questions

Question 1 of 5

You contain two odorous gases in vials with porous plugs. Gas A has twice the mass of Gas B. Which observation is most likely?

Correct Answer: A

Rationale: The correct answer is A because the rate of effusion of a gas is inversely proportional to the square root of its molar mass, assuming the same conditions. Since Gas A has twice the mass of Gas B, Gas B will effuse faster. Therefore, you will smell Gas A before you smell Gas B. Choice B is incorrect because Gas B will be smelled first due to its faster effusion rate. Choices C and D are incorrect because both gases will eventually be smelled due to their odorous nature, but the order of detection is based on effusion rates, not presence or absence of smell.

Question 2 of 5

What is the molarity of a solution containing 45 moles of NaCl in 4 liters?

Correct Answer: A

Rationale: To find molarity, divide moles of solute by liters of solution. In this case, molarity = 45 moles NaCl / 4 L = 11.25 M. However, NaCl is a salt, so you need to consider its formula weight (58.44 g/mol). Thus, 45 moles NaCl is 45 moles x 58.44 g/mol = 2634.6 g. Convert grams to kilograms (2634.6 g / 1000 = 2.6346 kg). Finally, molarity = 2.6346 kg / 4 L = 0.11 M NaCl. Choice A is correct because it accurately calculates the molarity. Choices B, C, and D are incorrect due to incorrect calculations.

Question 3 of 5

What is a pentose sugar?

Correct Answer: C

Rationale: The correct answer is C: A 5 carbon sugar. Pentose sugars are carbohydrates with 5 carbon atoms. They are essential components of nucleic acids like DNA and RNA. A is incorrect because it has 6 carbons, not 5. B is incorrect as it has 4 carbons. D is incorrect as it has 7 carbons, not 5. Therefore, the correct choice is C as it accurately describes a pentose sugar.

Question 4 of 5

Which two elements are most alike in reactivity?

Correct Answer: C

Rationale: The correct answer is C: Cl and P. Both chlorine (Cl) and phosphorus (P) are in the same group on the periodic table (Group 7A/17) and therefore have similar outer electron configurations. This results in similar reactivity patterns, such as forming covalent compounds. Choices A, B, and D are incorrect because they involve elements from different groups with different electron configurations and reactivity patterns. He (helium) and H (hydrogen) are both in different groups and have very different properties. K (potassium) and Ar (argon) are from different groups and have different reactivity levels. Ba (barium) and Mg (magnesium) are also from different groups and exhibit different reactivity behaviors.

Question 5 of 5

What is the correct formula for potassium chloride?

Correct Answer: B

Rationale: The correct formula for potassium chloride is KCl. "K" represents potassium and "Cl" represents chloride. Potassium is a metal with a +1 charge, while chloride is a non-metal with a -1 charge. When these two ions combine, they form a neutral compound with a 1:1 ratio, resulting in the formula KCl. Choice A (NaCl) is incorrect because "Na" represents sodium, not potassium. Choice C (KCl) is also incorrect because it is the same as the correct answer. Choice D (ClK) is incorrect as the order of elements in a chemical formula matters, and in this case, it should be KCl to represent potassium chloride accurately.

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