Q: Which of the following is the correct formula for calculating percent yield in a chemical reaction?

$$\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100$$

Question 1

Which of the following statements best describes the difference between mass number and atomic number for an element?

Accepted Answer

Atomic number is the number of protons, while mass number is the sum of protons and neutrons.

Question 2

A patient receives 250 mL of a saline solution. If the solution contains 0.9% NaCl by mass, how many grams of NaCl did the patient receive? (Assume the density of the solution is $$1.0 \ \mathrm{g/mL})$$

Accepted Answer

$$2.25 \ \mathrm{g}$$

Question 3

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have a full valence electron shell, making them stable.

Question 4

A chemical reaction releases $$150 \ \mathrm{kJ} of $$energy. Which of the following best describes this reaction?

Accepted Answer

It is an exothermic reaction because energy is released.

Question 5

Which of the following is the correct electron configuration for a neutral atom of oxygen ($$Z = 8$$)?

Accepted Answer

$$1s^2$$ \ $$2s^2$$ \ $$2p^4$$

Question 6

A solution is prepared by dissolving $$5.0 \ \mathrm{g} of $$glucose ($$C_6H_{12}O_6$) in enough water to make 100.0$$ \ \mathrm{mL}$$ of solution. What is the molarity of the solution? (Molar mass of glucose = 180.16$$ \ \mathrm{g/mol}$$)

Accepted Answer

$$0.278 \ \mathrm{M}$$

Question 7

Which of the following best describes the role of a buffer in a biological system?

Accepted Answer

A buffer maintains a stable pH by neutralizing small amounts of acid or base.

Question 8

Which of the following compounds is ionic?

Accepted Answer

$$NaCl$$

Question 9

A sample of gas occupies $$2.0 \ \mathrm{L} at$$ $$1.0 \ \mathrm{atm}$$ and $$300 \ \mathrm{K}. $$What will be its volume at $$2.0 \ \mathrm{atm}$$ and $$300 \ \mathrm{K}$$, assuming ideal gas behavior?

Accepted Answer

$$1.0 \ \mathrm{L}$$

Question 10

Which of the following is the correct balanced equation for the combustion of methane ($$CH_4$$)?

Accepted Answer

$$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$

Question 11

Which statement best explains why water is a polar molecule?

Accepted Answer

Water has a bent shape and unequal sharing of electrons due to oxygen's higher electronegativity.

Question 12

A solution is made by diluting $$50.0 \ \mathrm{mL} of$$ $$2.0 \ \mathrm{M}$$ NaOH to a final volume of $$200.0 \ \mathrm{mL}. $$What is the final concentration?

Accepted Answer

$$0.50 \ \mathrm{M}$$

Question 13

Which of the following best describes the process of osmosis?

Accepted Answer

Movement of solvent from low solute concentration to high solute concentration through a semipermeable membrane.

Question 14

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 15

Which of the following is the correct formula for calculating percent yield in a chemical reaction?

Accepted Answer

$$	ext{Percent Yield} = \frac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100$$

Question 16

A buffer solution is made by mixing $$0.10 \ \mathrm{mol} of $$acetic acid ($$CH_3COOH) $$and $$0.10 \ \mathrm{mol} of $$sodium acetate ($$CH_3COONa) in$$ $$1.0 \ \mathrm{L} of $$water. If a small amount of $$HCl is $$added, what will happen to the pH?

Accepted Answer

The pH will remain nearly constant.

Question 17

Which of the following is the correct formula for converting Celsius temperature to Kelvin?

Accepted Answer

$$K = ^\circ C + 273.15$$

Question 18

Which of the following best describes the VSEPR theory?

Accepted Answer

It predicts the shape of molecules based on electron pair repulsion.

Question 19

A student mixes $$100.0 \ \mathrm{mL} of$$ $$0.10 \ \mathrm{M}$$ $$HCl$$ with $$100.0 \ \mathrm{mL} of$$ $$0.10 \ \mathrm{M}$$ $$NaOH. $$What is the pH of the resulting solution?

Accepted Answer

pH $$= 7$$

Question 20

Which of the following best explains why carbon is able to form such a wide variety of organic compounds?

Accepted Answer

Carbon can form four covalent bonds and bond with many different elements.

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