HESI A2
HESI A2 Chemistry Practice Questions
1. Cobalt-60 has a half-life of 5 years. If you start with 20 g of cobalt-60, how much is left after 10 years?
- A. 15 g
- B. 10 g
- C. 5 g
- D. 2.5 g
Correct answer: C
Rationale: Cobalt-60's half-life of 5 years means that after 5 years, half of the initial amount remains. Therefore, after 10 years, a quarter (half of a half) of the initial amount will remain. Starting with 20 g, after 10 years, 5 g of cobalt-60 will be left. Choice A (15 g) is incorrect because it assumes a linear decrease, not considering the exponential decay characteristic of radioactive substances. Choice B (10 g) is incorrect as it overlooks that after 10 years, more decay has occurred. Choice D (2.5 g) is incorrect as it represents only an eighth of the initial amount after 10 years, not a quarter.
2. If he left a tip of $36 on a total bill of $200, what percentage of the total bill did he leave as a tip?
- A. 16%
- B. 18%
- C. 20%
- D. 22%
Correct answer: B
Rationale: To determine the tip percentage left, divide the tip amount ($36) by the total bill amount ($200), then multiply the result by 100 to express it as a percentage: (36/200) x 100 = 18%. Therefore, he left an 18% tip on the total bill amount. Choice A (16%) is incorrect because the correct calculation results in 18%. Choice C (20%) and Choice D (22%) are incorrect as they do not match the calculated percentage based on the provided numbers.
3. Change the following fraction into a ratio: 19/40
- A. 19:40
- B. 40:19
- C. 19:4
- D. 40:4
Correct answer: A
Rationale: To change a fraction into a ratio, you replace the fraction bar (/) with a colon (:). Therefore, 19/40 as a ratio is written as 19:40. Choice B (40:19) is incorrect as it reverses the order of the numbers. Choice C (19:4) is incorrect as it uses the denominator as the second number, which is not the correct way to represent a ratio. Choice D (40:4) is incorrect as it does not reflect the original fraction accurately.
4. Which, if any, of the following statements are true?
- A. Water boils at approximately 100°C (212°F) at standard atmospheric pressure
- B. The boiling point is the temperature at which the vapor pressure is higher than the atmospheric pressure around the water
- C. Water boils at a lower temperature in areas of lower pressure
- D. A and C are true
Correct answer: D
Rationale: Both statements A and C are true. Water indeed boils at approximately 100°C (212°F) at standard atmospheric pressure. However, water boils at a lower temperature in areas of lower pressure due to the decreased atmospheric pressure, which affects the vapor pressure and boiling point of water. Statement B is incorrect because the boiling point is the temperature at which the vapor pressure equals the external pressure (atmospheric pressure in this case), not when it is higher.
5. Which is the best title for this passage?
- A. “Medical Treatment for Gout”
- B. “Uric Acid Affects the Joints”
- C. “Risk Factors for One Type of Arthritis”
- D. “Nurse-Led Care Aids Gout Patients”
Correct answer: D
Rationale: The passage focuses on how nurse-led care, including holistic education and lifestyle advice, can aid patients with gout.
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