Q: A student needs to convert 5.00 kilometers to centimeters. Which of the following is the correct answer, and what is the dimensional analysis setup?

$$5.00 \, \text{km} \times \frac{1000 \, \text{m}}{1 \, \text{km}} \times \frac{100 \, \text{cm}}{1 \, \text{m}} = 5.00 \times 10^5$ \, \text{cm}$$

Question 1

Which of the following best describes the difference between a chemical property and a physical property?

Accepted Answer

A chemical property describes how a substance undergoes a chemical change, while a physical property can be observed without changing the substance's identity.

Question 2

A student needs to convert 5.00 kilometers to centimeters. Which of the following is the correct answer, and what is the dimensional analysis setup?

Accepted Answer

$$5.00 \, 	ext{km} 	imes \frac{1000 \, 	ext{m}}{1 \, 	ext{km}} 	imes \frac{100 \, 	ext{cm}}{1 \, 	ext{m}} = 5.00 	imes 10^5$ \, 	ext{cm}$$

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 4

A sample of gas at STP occupies 22.4 L. How many moles of gas are present?

Accepted Answer

$$1.00$$ mole

Question 5

Which of the following best explains why sodium (Na) reacts vigorously with water, while magnesium (Mg) does not?

Accepted Answer

Sodium has a lower ionization energy than magnesium, making it easier to lose its outer electron.

Question 6

Which of the following is the correct electron configuration for a neutral oxygen atom?

Accepted Answer

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

Question 7

A solution is prepared by dissolving 10.0 g of NaCl in enough water to make 500.0 mL of solution. What is the molarity of the solution? ($$	ext{Molar mass of NaCl} = 58.44 \, 	ext{g/mol})$$

Accepted Answer

$$0.342 \, 	ext{M}$$

Question 8

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst increases the rate of a reaction by lowering the activation energy.

Question 9

Which of the following compounds is named correctly?

Accepted Answer

FeCl$$_3 is $$named iron(III) chloride.

Question 10

A sample of calcium carbonate (CaCO$$_3) $$decomposes according to the equation: $$	ext{CaCO}_3 (s) ightarrow 	ext{CaO} (s) + 	ext{CO}_2 (g). If 50.0 g of $$CaCO$$_3 is $$heated, how many grams of CO$$_2$$ are produced? ($$	ext{Molar mass of CaCO}_3 = 100.1 \, 	ext{g/mol}$$, $$	ext{Molar mass of CO}_2 = 44.0 \, 	ext{g/mol})$$

Accepted Answer

$$22.0 \, 	ext{g}$$

Question 11

Which of the following statements about the periodic trends in atomic radius is correct?

Accepted Answer

Atomic radius increases down a group and decreases across a period.

Question 12

Which of the following best describes what happens during oxidation in a redox reaction?

Accepted Answer

An atom loses electrons.

Question 13

A 25.0 mL sample of 0.200 M HCl is titrated with 0.100 M NaOH. What volume of NaOH is required to reach the equivalence point?

Accepted Answer

$$50.0 \, 	ext{mL}$$

Question 14

Which of the following is the correct Lewis structure for carbon dioxide (CO$$_2$$)?

Accepted Answer

O=C=O, with each oxygen atom having two lone pairs.

Question 15

Which of the following best describes the effect of increasing temperature on the rate of a chemical reaction?

Accepted Answer

Increasing temperature increases the rate by providing more particles with enough energy to overcome the activation energy barrier.

Question 16

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

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

Question 17

Which of the following best describes the relationship between [H$$_3O$^+$$] and [OH$$^-$$] in pure water at 25$$^\circC$$?

Accepted Answer

$$[H_3O^+] 	imes [OH^-] = 1.0 	imes 10$$^{-14}$$

Question 18

A balloon contains 2.00 moles of helium gas at 1.00 atm and 273 K. What is the volume of the balloon? (Use the ideal gas law: $$PV = nRT$$, $$R = 0.0821 \, 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$44.8 \, 	ext{L}$$

Question 19

Which of the following best describes Le Chatelier's Principle?

Accepted Answer

If a system at equilibrium is disturbed, the system will shift to counteract the disturbance and restore equilibrium.

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