Q: A nutrition label states that a serving contains 10 g of carbohydrates, 6 g of fat, and 2 g of protein. What is the total caloric value of one serving? (Use: $$1 \text{ g carbohydrate} = 4 \text{ kcal}$$, $$1 \text{ g fat} = 9 \text{ kcal}$$, $$1 \text{ g protein} = 4 \text{ kcal})$$

$$(10 \times 4) + (6 \times 9) + (2 \times 4) = 40 + 54 + 8 = 102$$ kcal

Q: A 560 g sample of water cools from $$67^\circ \text{C} to$$ $$22^\circ \text{C}. $$How many kilocalories are lost? (Use: $$\text{SH}_{\text{water}} = 1.00 \text{ cal/g}^\circ \text{C}$$, $$1 \text{ kcal} = 1000 \text{ cal})$$

$$560 \times (67-22) \times 1.00 = 560 \times 45 = 25,200$$ cal $$= 25.2$$ kcal

Q: A 25.0 g sample of gold is heated from $$25^\circ \text{C} to$$ $$175^\circ \text{C}. $$The specific heat of gold is $$0.0308 \text{ cal/g}^\circ \text{C}. $$How many calories are required?

$$25.0 \times (175-25) \times 0.0308 = 25.0 \times 150 \times 0.0308 = 115.5$$ cal

Q: A sample of ethanol at $$25.0^\circ \text{C}$$ absorbs $$95.3$$ cal of heat. The specific heat of ethanol is $$0.586 \text{ cal/g}^\circ \text{C}$$ and the mass is $$10.0 g. $$What is the final temperature of the ethanol? (Use: $$q = m \times SH \times \Delta T)$$

$$\Delta T = \frac{q}{m \times SH} = \frac{95.3}{10.0 \times 0.586} = 16.3^\circ \text{C}$$; Final T = $$25.0 + 16.3 = 41.3^\circ \text{C}$$

Question 1

Which of the following statements best describes the difference between potential energy and kinetic energy?

Accepted Answer

Potential energy is stored energy, while kinetic energy is the energy of motion.

Question 2

A nutrition label states that a serving contains 10 g of carbohydrates, 6 g of fat, and 2 g of protein. What is the total caloric value of one serving? (Use: $$1 	ext{ g carbohydrate} = 4 	ext{ kcal}$$, $$1 	ext{ g fat} = 9 	ext{ kcal}$$, $$1 	ext{ g protein} = 4 	ext{ kcal})$$

Accepted Answer

$$(10 	imes 4) + (6 	imes 9) + (2 	imes 4) = 40 + 54 + 8 = 102$$ kcal

Question 3

How many kilojoules are equivalent to 250 Calories (nutritional)? (Use: $$1 	ext{ Cal} = 1 	ext{ kcal} = 4.184 	ext{ kJ})$$

Accepted Answer

$$250 	imes 4.184 = 1046 kJ$$

Question 4

Which of the following foods would provide the most energy per gram?

Accepted Answer

Fat

Question 5

A 560 g sample of water cools from $$67^\circ 	ext{C} to$$ $$22^\circ 	ext{C}. $$How many kilocalories are lost? (Use: $$	ext{SH}_{	ext{water}} = 1.00 	ext{ cal/g}^\circ 	ext{C}$$, $$1 	ext{ kcal} = 1000 	ext{ cal})$$

Accepted Answer

$$560 	imes (67-22) 	imes 1.00 = 560 	imes 45 = 25,200$$ cal $$= 25.2$$ kcal

Question 6

Which of the following intermolecular forces is the strongest?

Accepted Answer

Hydrogen bonds

Question 7

Which of the following molecules can form hydrogen bonds with itself?

Accepted Answer

NH$$_3$$

Question 8

A 25.0 g sample of gold is heated from $$25^\circ 	ext{C} to$$ $$175^\circ 	ext{C}. $$The specific heat of gold is $$0.0308 	ext{ cal/g}^\circ 	ext{C}. $$How many calories are required?

Accepted Answer

$$25.0 	imes (175-25) 	imes 0.0308 = 25.0 	imes 150 	imes 0.0308 = 115.5$$ cal

Question 9

Which of the following statements about boiling points is correct?

Accepted Answer

Compounds with similar molecular weights and higher dipole moments have higher boiling points.

Question 10

Which of the following pairs of compounds, when compared, will have the higher boiling point and why? (A) H$$_2O vs. H$_2S$$

Accepted Answer

H$$_2O$$, because it can form hydrogen bonds.

Question 11

Which of the following best explains why geckos can walk on walls and ceilings?

Accepted Answer

They use London dispersion forces between the tiny hairs on their feet and the surface.

Question 12

A sample of ethanol at $$25.0^\circ 	ext{C}$$ absorbs $$95.3$$ cal of heat. The specific heat of ethanol is $$0.586 	ext{ cal/g}^\circ 	ext{C}$$ and the mass is $$10.0 g. $$What is the final temperature of the ethanol? (Use: $$q = m 	imes SH 	imes \Delta T)$$

Accepted Answer

$$\Delta T = \frac{q}{m 	imes SH} = \frac{95.3}{10.0 	imes 0.586} = 16.3^\circ 	ext{C}$$; Final T = $$25.0 + 16.3 = 41.3^\circ 	ext{C}$$

Question 13

Which of the following best describes a London (dispersion) force?

Accepted Answer

A temporary attractive force that results from instantaneous dipoles in molecules.

Question 14

Which of the following statements about the relationship between molecular weight and boiling point is correct for compounds with similar dipole moments?

Accepted Answer

The compound with the higher molecular weight will have the higher boiling point.

Question 15

Which of the following compounds is nonpolar?

Accepted Answer

CO$$_2$$

Question 16

Which of the following best explains why DNA strands are held together?

Accepted Answer

Hydrogen bonds between complementary bases.

Question 17

Which of the following phase changes is endothermic?

Accepted Answer

Melting

Question 18

A snack contains 3 g of carbohydrate and 5 g of fat. How many kilocalories does it provide? (Use: $$1 	ext{ g carbohydrate} = 4 	ext{ kcal}$$, $$1 	ext{ g fat} = 9 	ext{ kcal})$$

Accepted Answer

$$(3 	imes 4) + (5 	imes 9) = 12 + 45 = 57$$ kcal

Energy, Matter, and Nutrition in Chemistry

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