Exam Review

How much heat is required to change 25.8 g of water from 35°C to 98°C? Specific heat of water is 4.18 J/g °C.

• 6780 J

• 4500 J

• 9000 J

• 12000 J

Answer explanation

To find the heat required, use the formula Q = mcΔT. Here, m = 25.8 g, c = 4.18 J/g°C, and ΔT = 98°C - 35°C = 63°C. Thus, Q = 25.8 g * 4.18 J/g°C * 63°C = 6780 J. Therefore, the correct answer is 6780 J.

Tags

NGSS.HS-PS3-4

What is the term for the transition of a material from a gas to a solid?

• Deposition

• Sublimation

• Condensation

• Evaporation

Answer explanation

The transition of a material from a gas directly to a solid is called deposition. This process occurs without passing through the liquid phase, unlike condensation, which involves gas to liquid.

Tags

NGSS.MS-PS1-4

Which states exist at the triple point of a substance?

• Solid, liquid, and gas

• Solid and liquid only

• Liquid and gas only

• Solid and gas only

Answer explanation

At the triple point of a substance, all three phases—solid, liquid, and gas—coexist in equilibrium. This unique condition allows for the simultaneous presence of these states, making 'Solid, liquid, and gas' the correct answer.

Substance A has a specific heat of 0.25 J/g°C, and substance B has a specific heat of 0.68 J/g°C. If both are initially at 25°C, when heated evenly, which will reach 50°C first?

• Substance A

• Substance B

• Both will reach at the same time

• Neither will reach 50°C

Answer explanation

Substance A has a lower specific heat (0.25 J/g°C) compared to substance B (0.68 J/g°C). This means substance A requires less energy to increase its temperature, allowing it to reach 50°C first.

Tags

NGSS.HS-PS3-4

How many calories are in a Big Mac? (33g fat, 44g carb and 25g protein)

Answer explanation

A Big Mac contains 563 calories. The correct answer is not provided in the choices, as '0' is not a valid calorie count for a Big Mac.

If someone ate a doughnut that contained 500 calories, how many hours would they have to exercise to use those calories if they were burning 125 calories per hour?

• 4 hours

• 2 hours

• 6 hours

• 8 hours

Answer explanation

To burn 500 calories at a rate of 125 calories per hour, divide 500 by 125. This gives 4 hours of exercise needed to use those calories, making 4 hours the correct answer.

A student mixed aluminum with hydrochloric acid and the temperature of the surrounding water increased by 25°C. Was the reaction endothermic or exothermic?

Answer explanation

The increase in temperature indicates that heat was released during the reaction. This means the reaction is exothermic, as exothermic reactions release energy, causing the surrounding temperature to rise.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

If a system has a pressure of 2.5 atm and a volume of 1.0 L, what is the new volume if the pressure increases to 7.5 atm?

• 0.33 L

• 0.13 L

• 0.75 L

• 2.0 L

Answer explanation

Using Boyle's Law (P1V1 = P2V2), we can calculate the new volume. With P1 = 2.5 atm, V1 = 1.0 L, and P2 = 7.5 atm, we find V2 = (P1V1)/P2 = (2.5 * 1.0) / 7.5 = 0.33 L. Thus, the new volume is 0.33 L.

How many moles are in a 2.5 L container if the pressure is 1.3 atm and the temperature is 298 K?

Answer explanation

Using the ideal gas law (PV=nRT), we can calculate moles (n). Here, P=1.3 atm, V=2.5 L, R=0.0821 L·atm/(K·mol), T=298 K. Solving gives n=0.13 moles. However, the correct answer is 0, indicating a possible error in the question.

What is the total pressure if a 5.0L container at a temperature of 425K contains 1.3 moles of oxygen and 2.6 moles of nitrogen?

• 16.4 atm

• 10.2 atm

• 22.8 atm

• 8.7 atm

Answer explanation

Using the ideal gas law, PV=nRT, we calculate total pressure. P = (nRT)/V. Here, n = 1.3 + 2.6 = 3.9 moles, R = 0.0821 L·atm/(K·mol), V = 5.0 L, T = 425 K. This gives P = 16.4 atm, the correct answer.