HESI A2
Chemistry Hesi A2 Questions
Question 1 of 5
A chemist takes 100 mL of a 40 g NaCl solution and dilutes it to 1L. What is the concentration (molarity) of the new solution?
Correct Answer: C
Rationale: Initially, the chemist has 40 g of NaCl in 100 mL of solution.
To find the initial molarity, we need to calculate the number of moles of NaCl using the molar mass of NaCl (58.44 g/mol). After dilution to 1 L, the molarity of the new solution can be calculated by dividing the moles of NaCl by the total volume in liters.
Therefore, the concentration (molarity) of the new solution is 0.40 M NaCl.
Choice A (0.04 M NaCl) is incorrect because it doesn't consider the correct molar concentration after dilution.
Choice B (0.25 M NaCl) is incorrect as it also doesn't account for the correct molar concentration post-dilution.
Choice D (2.5 M NaCl) is incorrect as it is too concentrated given the initial amount of NaCl and the dilution factor.
Question 2 of 5
Which of these intermolecular forces might represent attraction between atoms of a noble gas?
Correct Answer: B
Rationale: Noble gases are non-polar molecules without a permanent dipole moment. The only intermolecular force applicable to noble gases is the London dispersion force, also known as Van der Waals forces. This force is a temporary attractive force resulting from the formation of temporary dipoles in non-polar molecules. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding involve significant dipoles or hydrogen atoms bonded to electronegative atoms, which do not apply to noble gases.
Question 3 of 5
What are the products of combustion of a hydrocarbon in excess oxygen?
Correct Answer: A
Rationale: The correct answer is A: Carbon dioxide and water. During the combustion of a hydrocarbon in excess oxygen, the hydrocarbon reacts to produce carbon dioxide and water vapor as the final products. This reaction is known as complete combustion, where the hydrocarbon combines with oxygen to form carbon dioxide and water.
Choices B, C, and D are incorrect because naphthalene is a specific hydrocarbon compound, chlorine and bromine are not typically formed during the combustion of hydrocarbons in excess oxygen, and carbonium ions are not the products of this reaction.
Question 4 of 5
Why does fluorine have a higher ionization energy than oxygen?
Correct Answer: D
Rationale: Fluorine has a higher ionization energy than oxygen because fluorine has a larger nuclear charge. The greater number of protons in the nucleus of fluorine attracts its electrons more strongly, making it harder to remove an electron from a fluorine atom compared to an oxygen atom.
Choice A is incorrect as the number of neutrons does not directly affect ionization energy.
Choice B is also incorrect for the same reason.
Choice C is incorrect because a smaller nuclear charge would result in lower ionization energy, not higher.
Question 5 of 5
What does a blood sample with a pH of 3 indicate?
Correct Answer: A
Rationale: A blood pH of 3 is significantly low, indicating a strong acidity level. The normal blood pH range is 7.35 to 7.45; therefore, a pH of 3 is far below the normal range, showing a highly acidic condition in the blood sample.
Choice B is incorrect because a pH of 3 is not basic at all.
Choice C is incorrect as a pH of 3 is not weakly acidic but strongly acidic.
Choice D is wrong as a blood pH of 3 does not indicate a weakly basic condition.