Question 1

The dissolving of sodium acetate (NaC₂H₃O₂ = 82.04 g/mol) in water can be described by the following reaction: NaC₂H₃O₂ (s) $\rightarrow$NaC₂H₃O₂ (aq)$\Delta$H = -17.2 kJ How much heat will be released when 125 g of sodium acetate dissolve in water?

Accepted Answer

The heat released can be calculated using the molar heat of solution. First, find the number of moles of sodium acetate: $ \frac{125 \, \text{g}}{82.04 \, \text{g/mol}} = 1.523 \, \text{moles} $. Then, multiply the number of moles by the heat of solution per mole: $ 1.523 \, \text{moles} \times -17.2 \, \text{kJ/mol} = -26.2 \, \text{kJ} $.

Question 2

An industrial reactor has a heat capacity of 33,400 kJ/°C. How much will the temperature of the reactor rise if it absorbs 3.00 × 10⁵ kJ of heat energy?

Accepted Answer

The temperature rise can be calculated using the formula: Temperature rise = (Heat energy absorbed) / (Heat capacity) Substituting the given values, we get: Temperature rise = (3.00 × 10⁵ kJ) / (33,400 kJ/°C) Temperature rise = 8.98°C Therefore, the temperature of the reactor will rise by 8.98°C. Option C is the correct answer.

Question 3

The following reaction is an example of an _____ reaction. 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$H_rxn = +163.2 kJ

Accepted Answer

The positive value of the enthalpy change (+163.2 kJ) indicates that the reaction is absorbing heat from the surroundings, therefore it is an endothermic reaction.

Question 4

Water has a relatively high specific heat compared to metals. If a 20-g piece of a nonreactive metal at 80 °C is dropped into 20 g of cool water at 20 °C, what will be the final temperature of water and metal together?

Accepted Answer

Water has a higher specific heat capacity than metals, meaning it requires more energy to change its temperature. When a hot metal is placed in cooler water, the metal will lose heat while the water gains heat until thermal equilibrium is reached. The final temperature will be between the initial temperatures of the metal and the water, but closer to the water's initial temperature due to water's higher specific heat capacity.

Question 5

Consider the following reaction. How much heat is released if 5.00 moles of potassium react with excess chlorine? 2 K _(s) + Cl₂ _(g) $\rightarrow$2 KCl _(g) $\Delta$H_rxn = -873.0 kJ

Accepted Answer

The reaction shows that 2 moles of potassium react to release 873.0 kJ of heat. For 5 moles of potassium, the heat released would be (5 moles / 2 moles) * -873.0 kJ = -2,182.5 kJ, which rounds to -2,180 kJ, matching option D.

Question 6

When a metal object is dropped into cold water, it releases 4,715 J of energy to its surroundings, and its temperature decreases from 100.0 °C to 20.0 °C. The mass of the object is 420 grams. What is the specific heat of this material?

Accepted Answer

We can use the equation for heat energy:

q = mCΔT

Where:
q = heat energy released (-4715 J)
m = mass (0.420 kg or 420 g)
C = specific heat (unknown)
ΔT = change in temperature (100-20=80 °C)

Substituting the given values:

-4715 J = (0.420 kg)C(80 °C)

Simplifying:

C = -4715 J / (0.420 kg)(80 °C)
C = -14.02 J/(g·°C)

We get a negative value for C because the temperature of the object decreased. However, we need to report a positive value for specific heat. So we take the absolute value:

C = 14.02 J/(g·°C)

Rounding to the correct number of significant figures, we get:

C = 0.140 J/g·°C

Therefore, the best answer choice is C.

Question 7

When a liquid evaporates, it absorbs heat from its surroundings. This is a(n) _____ process.

Accepted Answer

During evaporation, molecules at the surface of the liquid gain enough energy to break their intermolecular bonds and become a gas. This requires energy, which is absorbed from the surroundings, making it an endothermic process.

Question 8

The fuel value of propane is 50.3 kJ/g. How much heat results from the combustion of 2.84 kg of propane? (Watch your units!)

Accepted Answer

To calculate the heat resulting from the combustion of propane, we need to use the formula:

Q = m x ΔHf

where:
- Q is the heat released (in kJ)
- m is the mass of propane burned (in g or kg)
- ΔHf is the heat of combustion of propane (in kJ/g)

Let's convert the mass given in the problem to grams:

2.84 kg = 2.84 x 1000 g/kg = 2840 g

Now we can plug in the values:

Q = 2840 g x 50.3 kJ/g

Q = 143,012 kJ

Therefore, the heat resulting from the combustion of 2.84 kg of propane is 143,000 kJ. The answer is B.

Question 9

The following reaction is an example of an _____ reaction. 2 K (s) + Cl₂ (g) $\rightarrow$2 KCl (g)$\Delta$H_rxn = -873.0 kJ

Accepted Answer

The negative delta H value (-873.0 kJ) indicates that heat is being released, making the reaction exothermic.

Question 10

If the reaction below absorbs 1,350 kJ of energy, how many grams of N₂O will be produced? (N₂O = 44.0 g/mol) 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g)$\Delta$H_rxn = +163.2 kJ

Accepted Answer

Using the given thermochemical equation, we can see that the production of 2 moles of N₂O results in the absorption of 163.2 kJ of energy. Therefore, the production of 1 mole of N₂O requires the absorption of 81.6 kJ of energy. To absorb 1350 kJ of energy, we need to divide 1350 kJ by 81.6 kJ/mol to get the number of moles of N₂O produced. 1350 kJ ÷ 81.6 kJ/mol ≈ 16.54 mol of N₂O Finally, we can convert moles to grams using the molar mass: 16.54 mol × 44.0 g/mol ≈ 728 g N₂O Therefore, the answer is A) 728 g.

Question 11

If the reaction below produces 5,230 kJ of energy, how many grams of KCl will be produced? (KCl = 74.6 g/mol) 2 K (s) + Cl₂ (g) $\rightarrow$ 2 KCl _(g) $\Delta$H_rxn = -873.0 kJ

Accepted Answer

The reaction releases 873.0 kJ per 2 moles of KCl. To produce 5,230 kJ, the amount of KCl produced can be calculated by setting up a proportion based on the stoichiometry of the reaction and the molar mass of KCl. $5230 kJ * \frac{2 moles KCl}{873.0 kJ} * 74.6 g/mole = 894 g$.

Question 12

The fuel value of natural gas is 54.0 kJ/g. How much heat results from the combustion of 2.84 kg of natural gas? (Watch your units!)

Accepted Answer

First, we need to convert the mass from kg to g:

2.84 kg = 2,840 g

Next, we can use the formula:

heat = fuel value x mass

Plugging in the given values:

heat = 54.0 kJ/g x 2,840 g = 153,360 kJ

Rounding to three significant figures:

heat = 153,000 kJ

Therefore, the answer is B, which is the only choice that matches the calculated heat value.

Question 13

A bomb calorimeter has a heat capacity of 25.6 kJ/°C. How much will the temperature of the calorimeter rise if it absorbs 455 kJ of heat energy?

Accepted Answer

The heat absorbed by the calorimeter can be calculated using the equation:

Q = CΔT

where Q is the heat absorbed, C is the heat capacity, and ΔT is the change in temperature. Rearranging this equation to solve for ΔT gives:

ΔT = Q / C

Substituting the given values, we get:

ΔT = (455 kJ) / (25.6 kJ/°C) = 17.8 °C

Therefore, the temperature of the calorimeter will rise by 17.8 °C.

Question 14

What is the specific heat of copper if a 55.0-g sample absorbs 1,590 J of heat to raise its temperature by 75.0 °C?

Accepted Answer

The specific heat formula is:

q = mcΔT

Where q is the heat absorbed, m is the mass of the substance, c is the specific heat, and ΔT is the change in temperature.

Plugging in the values given in the problem:

1,590 J = (55.0 g)(c)(75.0 °C)

Solving for c:

c = 0.385 J/g °C

Therefore, the answer is choice A.

Question 15

Consider the following reaction. How much heat is absorbed if 5.00 moles of nitrogen react with excess oxygen? 2 N₂ (g) + O₂ (g) $\rightarrow$2 N₂O (g)$\Delta$H_rxn = +163.2 kJ

Accepted Answer

The answer of Consider the following reaction. How much heat...

Question 16

The dissolving of ammonium nitrate (NH₄NO₃ = 80.06 g/mol) in water can be described by the following reaction: NH₄NO₃ (s) $\rightarrow$NH₄NO₃ (aq)$\Delta$H = +25.4 kJ How much heat will be absorbed when 175 g of sodium acetate dissolve in water?

Accepted Answer

The heat absorbed can be calculated using the given enthalpy change and the mass of the substance. Given that the enthalpy change for dissolving ammonium nitrate is +25.4 kJ per mole, and the molar mass is 80.06 g/mol, for 175 g of the substance, the calculation is as follows: (175 g / 80.06 g/mol) * 25.4 kJ/mol = 55.5 kJ.

Question 17

When a gas condenses, it releases heat to its surroundings. This is a(n) _____ process.

Accepted Answer

Exothermic processes release heat to the surroundings, while endothermic processes absorb heat from the surroundings. The other two options, thermoneutral and exergetic, are not related to the release or absorption of heat during a process.

Question 18

What is the specific heat of tin if a 55.0-g sample absorbs 982 J of heat to raise its temperature by 85.0 °C?

Accepted Answer

The specific heat (c) can be calculated using the formula $q = mc\Delta T$, where $q$ is the heat absorbed, $m$ is the mass, and $\Delta T$ is the change in temperature. Rearranging for $c$, we get $c = \frac{q}{m\Delta T}$. Plugging in the given values, $c = \frac{982 \, \text{J}}{55.0 \, \text{g} \times 85.0 \, \text{°C}} = 0.210 \, \text{J/g °C}$.

Question 19

The fuel value of propane is 50.3 kJ/g. If a full barbecue grill tank holds 9.0 kg, how much heat results from the complete combustion of all the propane? (Watch your units!)

Accepted Answer

To find the total heat resulting from the complete combustion of all the propane, we need to multiply the amount of propane by its fuel value:

Heat = fuel value × amount of propane

The amount of propane is given in kilograms, so we need to convert it to grams to match the units of the fuel value:

Amount of propane = 9.0 kg × 1000 g/kg = 9000 g

Now we can calculate the total heat:

Heat = 50.3 kJ/g × 9000 g = 452,700 kJ

Therefore, the correct answer is B.

Quiz 8: Energy

The dissolving of sodium acetate (NaC₂H₃O₂ = 82.04 g/mol) in water can be described by the following reaction: NaC₂H₃O₂ (s) $\rightarrow$ NaC₂H₃O₂ (aq) $\Delta$ H = -17.2 kJ How much heat will be released when 125 g of sodium acetate dissolve in water?

An industrial reactor has a heat capacity of 33,400 kJ/°C. How much will the temperature of the reactor rise if it absorbs 3.00 × 10⁵ kJ of heat energy?

The following reaction is an example of an _____ reaction. 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$ H_rxn = +163.2 kJ

Water has a relatively high specific heat compared to metals. If a 20-g piece of a nonreactive metal at 80 °C is dropped into 20 g of cool water at 20 °C, what will be the final temperature of water and metal together?

Consider the following reaction. How much heat is released if 5.00 moles of potassium react with excess chlorine? 2 K _(s) + Cl₂ _(g) $\rightarrow$ 2 KCl _(g) $\Delta$ H_rxn = -873.0 kJ

When a metal object is dropped into cold water, it releases 4,715 J of energy to its surroundings, and its temperature decreases from 100.0 °C to 20.0 °C. The mass of the object is 420 grams. What is the specific heat of this material?

When a liquid evaporates, it absorbs heat from its surroundings. This is a(n) _____ process.

The fuel value of propane is 50.3 kJ/g. How much heat results from the combustion of 2.84 kg of propane? (Watch your units!)

The following reaction is an example of an _____ reaction. 2 K (s) + Cl₂ (g) $\rightarrow$ 2 KCl (g) $\Delta$ H_rxn = -873.0 kJ

If the reaction below absorbs 1,350 kJ of energy, how many grams of N₂O will be produced? (N₂O = 44.0 g/mol) 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$ H_rxn = +163.2 kJ

If the reaction below produces 5,230 kJ of energy, how many grams of KCl will be produced? (KCl = 74.6 g/mol) 2 K (s) + Cl₂ (g) $\rightarrow$ 2 KCl _(g) $\Delta$ H_rxn = -873.0 kJ

The fuel value of natural gas is 54.0 kJ/g. How much heat results from the combustion of 2.84 kg of natural gas? (Watch your units!)

A bomb calorimeter has a heat capacity of 25.6 kJ/°C. How much will the temperature of the calorimeter rise if it absorbs 455 kJ of heat energy?

What is the specific heat of copper if a 55.0-g sample absorbs 1,590 J of heat to raise its temperature by 75.0 °C?

Consider the following reaction. How much heat is absorbed if 5.00 moles of nitrogen react with excess oxygen? 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$ H_rxn = +163.2 kJ

The dissolving of ammonium nitrate (NH₄NO₃ = 80.06 g/mol) in water can be described by the following reaction: NH₄NO₃ (s) $\rightarrow$ NH₄NO₃ (aq) $\Delta$ H = +25.4 kJ How much heat will be absorbed when 175 g of sodium acetate dissolve in water?

When a gas condenses, it releases heat to its surroundings. This is a(n) _____ process.

What is the specific heat of tin if a 55.0-g sample absorbs 982 J of heat to raise its temperature by 85.0 °C?

The fuel value of propane is 50.3 kJ/g. If a full barbecue grill tank holds 9.0 kg, how much heat results from the complete combustion of all the propane? (Watch your units!)

Quiz 8: Energy

The dissolving of sodium acetate (NaC2H3O2 = 82.04 g/mol) in water can be described by the following reaction: NaC2H3O2 (s) →\rightarrow→ NaC2H3O2 (aq) Δ\DeltaΔ H = -17.2 kJ How much heat will be released when 125 g of sodium acetate dissolve in water?

An industrial reactor has a heat capacity of 33,400 kJ/°C. How much will the temperature of the reactor rise if it absorbs 3.00 × 105 kJ of heat energy?

The following reaction is an example of an _____ reaction. 2 N2 (g) + O2 (g) →\rightarrow→ 2 N2O (g) Δ\DeltaΔ Hrxn = +163.2 kJ

Water has a relatively high specific heat compared to metals. If a 20-g piece of a nonreactive metal at 80 °C is dropped into 20 g of cool water at 20 °C, what will be the final temperature of water and metal together?

Consider the following reaction. How much heat is released if 5.00 moles of potassium react with excess chlorine? 2 K (s) + Cl2 (g) →\rightarrow→ 2 KCl (g) Δ\DeltaΔ Hrxn = -873.0 kJ

When a metal object is dropped into cold water, it releases 4,715 J of energy to its surroundings, and its temperature decreases from 100.0 °C to 20.0 °C. The mass of the object is 420 grams. What is the specific heat of this material?

When a liquid evaporates, it absorbs heat from its surroundings. This is a(n) _____ process.

The fuel value of propane is 50.3 kJ/g. How much heat results from the combustion of 2.84 kg of propane? (Watch your units!)

The following reaction is an example of an _____ reaction. 2 K (s) + Cl2 (g) →\rightarrow→ 2 KCl (g) Δ\DeltaΔ Hrxn = -873.0 kJ

If the reaction below absorbs 1,350 kJ of energy, how many grams of N2O will be produced? (N2O = 44.0 g/mol) 2 N2 (g) + O2 (g) →\rightarrow→ 2 N2O (g) Δ\DeltaΔ Hrxn = +163.2 kJ

If the reaction below produces 5,230 kJ of energy, how many grams of KCl will be produced? (KCl = 74.6 g/mol) 2 K (s) + Cl2 (g) →\rightarrow→ 2 KCl (g) Δ\DeltaΔ Hrxn = -873.0 kJ

The fuel value of natural gas is 54.0 kJ/g. How much heat results from the combustion of 2.84 kg of natural gas? (Watch your units!)

A bomb calorimeter has a heat capacity of 25.6 kJ/°C. How much will the temperature of the calorimeter rise if it absorbs 455 kJ of heat energy?

What is the specific heat of copper if a 55.0-g sample absorbs 1,590 J of heat to raise its temperature by 75.0 °C?

Consider the following reaction. How much heat is absorbed if 5.00 moles of nitrogen react with excess oxygen? 2 N2 (g) + O2 (g) →\rightarrow→ 2 N2O (g) Δ\DeltaΔ Hrxn = +163.2 kJ

The dissolving of ammonium nitrate (NH4NO3 = 80.06 g/mol) in water can be described by the following reaction: NH4NO3 (s) →\rightarrow→ NH4NO3 (aq) Δ\DeltaΔ H = +25.4 kJ How much heat will be absorbed when 175 g of sodium acetate dissolve in water?

When a gas condenses, it releases heat to its surroundings. This is a(n) _____ process.

What is the specific heat of tin if a 55.0-g sample absorbs 982 J of heat to raise its temperature by 85.0 °C?

The fuel value of propane is 50.3 kJ/g. If a full barbecue grill tank holds 9.0 kg, how much heat results from the complete combustion of all the propane? (Watch your units!)

The dissolving of sodium acetate (NaC₂H₃O₂ = 82.04 g/mol) in water can be described by the following reaction: NaC₂H₃O₂ (s) $\rightarrow$ NaC₂H₃O₂ (aq) $\Delta$ H = -17.2 kJ How much heat will be released when 125 g of sodium acetate dissolve in water?

An industrial reactor has a heat capacity of 33,400 kJ/°C. How much will the temperature of the reactor rise if it absorbs 3.00 × 10⁵ kJ of heat energy?

The following reaction is an example of an _____ reaction. 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$ H_rxn = +163.2 kJ

Consider the following reaction. How much heat is released if 5.00 moles of potassium react with excess chlorine? 2 K _(s) + Cl₂ _(g) $\rightarrow$ 2 KCl _(g) $\Delta$ H_rxn = -873.0 kJ

The following reaction is an example of an _____ reaction. 2 K (s) + Cl₂ (g) $\rightarrow$ 2 KCl (g) $\Delta$ H_rxn = -873.0 kJ

If the reaction below absorbs 1,350 kJ of energy, how many grams of N₂O will be produced? (N₂O = 44.0 g/mol) 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$ H_rxn = +163.2 kJ

If the reaction below produces 5,230 kJ of energy, how many grams of KCl will be produced? (KCl = 74.6 g/mol) 2 K (s) + Cl₂ (g) $\rightarrow$ 2 KCl _(g) $\Delta$ H_rxn = -873.0 kJ

Consider the following reaction. How much heat is absorbed if 5.00 moles of nitrogen react with excess oxygen? 2 N₂ (g) + O₂ (g) $\rightarrow$ 2 N₂O (g) $\Delta$ H_rxn = +163.2 kJ

The dissolving of ammonium nitrate (NH₄NO₃ = 80.06 g/mol) in water can be described by the following reaction: NH₄NO₃ (s) $\rightarrow$ NH₄NO₃ (aq) $\Delta$ H = +25.4 kJ How much heat will be absorbed when 175 g of sodium acetate dissolve in water?