Q: You are asked to make a 2 Molar solution of Potassium Dichromate (K2Cr2O7) using 1 liter of water. What is the mass of K2Cr2O7 required? (Atomic masses: K = 39, Cr = 52, O = 16)

$$2 \times (2 \times 39 + 2 \times 52 + 7 \times 16) = 2 \times 294 = 588$$ grams

Q: A colleague asks you to make a 1.5 Molar solution of Sodium Nitrate (NaNO3) in 2 liters of water. What mass of NaNO3 do you need? (Atomic masses: Na = 23, N = 14, O = 16)

$$1.5 \times 2 \times (23 + 14 + 3 \times 16) = 3 \times 71 = 213$$ grams

Q: You are asked to make a 4 Molar solution of Sodium Nitrate (NaNO3) using 150 g of the substance. How much water do you need? (Molecular weight of NaNO3 = 85 g/mol)

$$\text{Volume} = \frac{\text{mass}}{\text{molarity} \times \text{molecular weight}} = \frac{150}{4 \times 85} = 0.44 L$$

Q: A solution is prepared by dissolving 10 g of NaCl in enough water to make 500 mL of solution. What is the molarity of the solution? (Molecular weight of NaCl = 58.5 g/mol)

$$\text{Molarity} = \frac{\text{moles}}{\text{liters}} = \frac{10/58.5}{0.5} = 0.34 M$$

Q: If you have 0.5 moles of glucose (C6H12O6), how many grams do you have? (Molecular weight: C = 12, H = 1, O = 16)

$$0.5 \times (6 \times 12 + 12 \times 1 + 6 \times 16) = 0.5 \times 180 = 90$$ grams

Question 1

You are asked to make a 2 Molar solution of Potassium Dichromate (K2Cr2O7) using 1 liter of water. What is the mass of K2Cr2O7 required? (Atomic masses: K = 39, Cr = 52, O = 16)

Accepted Answer

$$2 	imes (2 	imes 39 + 2 	imes 52 + 7 	imes 16) = 2 	imes 294 = 588$$ grams

Question 2

A colleague asks you to make a 1.5 Molar solution of Sodium Nitrate (NaNO3) in 2 liters of water. What mass of NaNO3 do you need? (Atomic masses: Na = 23, N = 14, O = 16)

Accepted Answer

$$1.5 	imes 2 	imes (23 + 14 + 3 	imes 16) = 3 	imes 71 = 213$$ grams

Question 3

You are asked to make a 4 Molar solution of Sodium Nitrate (NaNO3) using 150 g of the substance. How much water do you need? (Molecular weight of NaNO3 = 85 g/mol)

Accepted Answer

$$	ext{Volume} = \frac{	ext{mass}}{	ext{molarity} 	imes 	ext{molecular weight}} = \frac{150}{4 	imes 85} = 0.44 L$$

Question 4

Which of the following best describes how acids and bases work?

Accepted Answer

Acids donate protons (H+) and bases accept protons (H+)

Question 5

Which of the following is an example of a base?

Accepted Answer

NaOH (Sodium Hydroxide)

Question 6

What is the process of evaporative cooling?

Accepted Answer

When water evaporates, the molecules with the highest kinetic energy leave, lowering the temperature of the remaining liquid.

Question 7

How does water moderate temperature on Earth?

Accepted Answer

Water has a high specific heat, so it absorbs and releases heat slowly, stabilizing temperatures.

Question 8

Which property of water explains why ice floats?

Accepted Answer

Ice is less dense than liquid water due to hydrogen bonding.

Question 9

A solution is prepared by dissolving 10 g of NaCl in enough water to make 500 mL of solution. What is the molarity of the solution? (Molecular weight of NaCl = 58.5 g/mol)

Accepted Answer

$$	ext{Molarity} = \frac{	ext{moles}}{	ext{liters}} = \frac{10/58.5}{0.5} = 0.34 M$$

Question 10

Which of the following best explains why water is an effective solvent?

Accepted Answer

Water is polar, allowing it to dissolve ionic and polar substances.

Question 11

If you have 0.5 moles of glucose (C6H12O6), how many grams do you have? (Molecular weight: C = 12, H = 1, O = 16)

Accepted Answer

$$0.5 	imes (6 	imes 12 + 12 	imes 1 + 6 	imes 16) = 0.5 	imes 180 = 90$$ grams

Question 12

Which of the following is a consequence of water's high heat of vaporization?

Accepted Answer

Sweating cools the body efficiently because water absorbs a lot of heat before evaporating.

Question 13

Which of the following statements about acids and bases is correct?

Accepted Answer

A solution with pH 3 is acidic and a solution with pH 11 is basic.

Question 14

Which of the following best describes the molecular structure of water?

Accepted Answer

Water is a polar molecule with a bent shape due to unequal sharing of electrons.

Question 15

Which of the following is a real-world example of water's ability to moderate temperature?

Accepted Answer

Coastal regions have milder climates than inland regions due to water's high specific heat.

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