Nursing Elites

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. How many pairs of electrons are shared between two atoms in a single bond?

• A. 1
• B. 2
• C. 3
• D. 4

Correct answer: A

Rationale: In a single bond, two atoms share one pair of electrons. This shared pair of electrons is what holds the atoms together in the bond. Therefore, the correct answer is A: 1. Choices B, C, and D are incorrect because they do not represent the number of electron pairs shared in a single bond.

3. Which state of matter has a definite volume but takes the shape of its container?

• A. Gas
• B. Liquid
• C. Solid
• D. Plasma

Correct answer: B

Rationale: The state of matter that has a definite volume but takes the shape of its container is a 'Liquid.' Liquids have a fixed volume but can change their shape to fit the container they are in. This property distinguishes liquids from solids, which have both a definite shape and volume, and gases, which do not have a fixed volume or shape. Therefore, the correct answer is 'Liquid.' Choice A, 'Gas,' is incorrect because gases do not have a definite volume or shape. Choice C, 'Solid,' is incorrect as solids have a definite shape and volume. Choice D, 'Plasma,' is incorrect because plasma is a state of matter where atoms have been ionized and do not have a fixed volume or shape.

4. Which two functional groups would you expect an amino acid to contain?

• A. R-NH2 and R-COOH
• B. R-CHO and R-CO-NH
• C. R-OH and R-COOR
• D. R-O-R and R-COOH

Correct answer: A

Rationale: Amino acids are organic compounds that are characterized by the presence of an amino group (NH2) and a carboxylic acid group (COOH) in their chemical structure. These two functional groups, found in option A, are fundamental components of amino acids and play crucial roles in their classification and biological functions. Option B contains an aldehyde group (CHO) and an amide group (CO-NH), which are not characteristic functional groups of amino acids. Option C includes a hydroxyl group (OH) and an ester group (COOR), which are not typically present in amino acids. Option D presents ether (R-O-R) and carboxylic acid (COOH) functional groups, which do not represent the functional groups commonly found in amino acids.

5. What is the role of a catalyst in a chemical reaction?

• A. Slows down the reaction
• B. Has no effect
• C. Speeds up the reaction
• D. Stops the reaction

Correct answer: C

Rationale: A catalyst speeds up a chemical reaction by lowering the activation energy required for the reaction to occur. It does not get consumed in the reaction and remains unchanged at the end, allowing it to facilitate multiple reaction cycles. Choice A is incorrect because a catalyst actually speeds up the reaction. Choice B is incorrect because catalysts do have an effect by accelerating the reaction. Choice D is incorrect because catalysts do not stop the reaction, but rather increase the reaction rate.

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