Chapter 7 Homework Flashcards

What is the first law of thermodynamics?

If the system of a chemical reaction gained 50 kJ of energy per mole what must also be true?

Convert 241 Calories to joules.

Hint: The unit Calories is a CAPITAL C.

1 calorie = 4.184 joules

1 Calorie = 1000 calories

Do not type units with your answer.

Convert 85.0 kJ to calories.

Hint: Notice the little c in calories.

1 calorie = 4.184 joules

1 Calorie = 1000 calories

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During a certain chemical reaction 1,150 J of heat is released from the system and 285 J of work is done on the surroundings. Calculate the change in internal energy of the system.

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During a certain chemical reaction 215 J of heat is absorbed by the system and 440 J of work is done on the surroundings. Calculate the change in internal energy of the system.

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Which of the following processes are exothermic? Mark all correct answers.

• Water condensing from steam to a liquid
• Water freezing from a liquid to a solid
• Water evaporating from a liquid to a gas
• Water melting from a solid to a liquid

How many grams of natural gas (CH₄) must burn to emit -299 kJ of heat?

CH₄ + 2O₂ --> CO + 2H₂O ΔH = -802 kJ/mol

OR

C H4 + 2 O2 right arrow CO + 2H2 O Delta H = -802 kJ/mol

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Type your answer to three significant figures.

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How many grams of oxygen gas must burn to emit -229 kJ of heat?

CH₄ + 2O₂ --> CO + 2H₂O ΔH = -802 kJ/mol

OR

C H4 + 2 O2 right arrow CO + 2H2 O Delta H = -802 kJ/mol

Do not type units with your answer.

Type your answer to three significant figures.

If this question is on an exam on your scrap paper report your answer to the proper number of significant figures but still type three significant figures online.

How much heat (in kJ) is released when 170 grams of CH₄ is burned with 2000. grams of O₂? If the answer is exothermic be sure your answer has the correct sign!

CH₄ + 2O₂ --> CO + 2H₂O ΔH = -802 kJ/mol

OR

C H4 + 2 O2 right arrow CO + 2H2 O Delta H = -802 kJ/mol

Hint: Determine the limiting reagent.

Do not type units with your answer.

Type your answer to three significant figures.

If this question is on an exam on your scrap paper report your answer to the proper number of significant figures but still type three significant figures online.

A silver block, initially at 50.0 °C, is submerged into 100.0 grams of water at 25.2 °C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 28.0°C. What is the mass of the silver block?

The specific heat capacity of silver is 0.235 J/g°C

The specific heat capacity of water is 4.184 J/g°C

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Type your answer to four significant figures.

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Two pieces of metal (A and B) are in contact with each other and initially at different temperatures. Metal A has a mass of 7.50 grams and an initial temperature of 22ºC and metal B has a mass of 12.25 grams and an initial temperature of 50ºC. When the two metals reach thermal equilibrium they have a final temperature of 35ºC. If metal A has a specific heat capacity of 1.25 J/gºC what is the specific heat capacity of metal B?

Remember:

-q for metal A = q for metal B and q = msΔT

Do not type units with your answer.

Type your answer to three significant figures.

If this question is on an exam on your scrap paper report your answer to the proper number of significant figures but still type three significant figures online.

Zinc metal reacts with HCl according to the following balanced equation:

Zn(s) + 2HCl(aq) --> ZnCl₂(aq) + H₂(g)

When 0.100 grams of Zn(s) is combined with an excess amount of HCl to make 52.0 mL of solution in a coffee-cup calorimeter, all the zinc reacts, raising the temperature of the solution from 22.40ºC to 24.90ºC. Find ΔH for this reaction in kJ/mol.

Assume the density of the solution is 1.00 g/mL and the specific heat capacity of the solution is 4.184 J/gºC.

Use an atomic weight of 65.38 g/mol for Zn

Hints:

-q(reaction) = q(solution)

ΔH = q/mol of limiting reagent

Do not type units with your answer.

Type your answer to three significant figures.

If this question is on an exam on your scrap paper report your answer to the proper number of significant figures but still type three significant figures online.

Use standard enthalpies of formation to calculate ΔHº_rxn for the following chemical reaction:

3NO₂ (g) + H₂O (l) --> 2HNO₃(aq) + NO(g)

OR

3 N" O₂ left parenthesis g right parenthesis + H₂O left parenthesis l right parenthesis right arrow 2H "N" O₃ left parenthesis aq right parenthsis + "N" O left parenthssis g right parenthesis

Given:

Species ΔH_f (kJ/mol)
N O₂ 33.2

H₂ O -285.8

H N O₃ -207

N O 91.3

Do not type any units with your answer. If the answer is exothermic be sure to include the appropriate sign. Report your answer to 1 decimal place.

Consider the problem below:

(Equation 1) H_2(g) + 1/2 O_{2 (g)} ---> H₂O_(l) ΔH = -285.8 kJ/mol

(Equation 2) C_(s) + O_2(g) ---> CO_2(g) ΔH = -393.5 kJ/mol

(Equation 3) 2 C_(s) + H_2(g) ---> C₂H_2(g) ΔH = 226.7 kJ/mol

(Equation 4) 2 C₂H_2(g) + 5 O_2(g) ---> 4 CO_2(g) + 2 H₂O_(l) ΔH = ???????

To find ΔH for equation 4 you must:

Screen Reader Version

Consider the problem below:

(Equation 1) H_2(g) + 1/2 O_{2 (g)} arrow H₂O_(l) ΔH = minus 285.8 kJ/mol

(Equation 2) C_(s) + O_{2(g) arrow} CO_2(g) ΔH = minus 393.5 kJ/mol

(Equation 3) 2 C_(s) + H_{2(g) arrow} C₂H_2(g) ΔH = 226.7 kJ/mol

(Equation 4) 2 C₂H_2(g) + 5 O_2(g) arrow 4 CO_2(g) + 2 H₂O_(l) ΔH = ???????

To find ΔH for equation 4 you must:

Consider the problem below:

(Equation 1) 2 Ca_(s) + O_2(g) ---> 2 CaO_(s) ΔH = -1270.2 kJ

(Equation 2) 4 Zn_(s) + 2 O_2(g) ---> 4 ZnO_(s) ΔH = -696.6 kJ

(Equation 3) 4 Ca_(s) + 4 ZnO_(s) ---> 4 Zn_(s) + 4 CaO_(s) ΔH = ???

To find ΔH for equation 3 you must:

Screen Reader Version

Consider the problem below:

(Equation 1) 2 "C"a_(s) + O_{2(g) arrow} 2 "C" a O_(s) ΔH = minus 1270.2 kJ

(Equation 2) 4 Zn_(s) + 2 O_{2(g) arrow} 4 Z n O_(s) ΔH = minus 696.6 kJ

(Equation 3) 4 "C"a_(s) + 4 Z n O_(s) arrow 4 Zn_(s) + 4 "C"a O_(s) ΔH = ???

To find ΔH for equation 3 you must:

Consider the problem below:

(Equation 1) 2 HF_(g) ---> H_2(g) + F_{2 (g)} ΔH = 537 kJ/mol

(Equation 2) C_(s) + 2 F_{2 (g)} ---> CF_{4 (g)} ΔH = -680. kJ/mol

(Equation 3) 2 C_(s) + 2 H_{2 (g)} ---> C₂H_4(g) ΔH = 52.3 kJ/mol

(Equation 4) C₂H_4(g) + 6 F_2(g) ---> 2 CF_4(g) + 4 HF_(g) ΔH = ???????

To find ΔH for equation 4 you must:

Screen Reader Version

Consider the problem below:

(Equation 1) 2 HF_(g) arrow H_2(g) + F_{2 (g)} ΔH = 537 kJ/mol

(Equation 2) C_(s) + 2 F_{2 (g)} arrow CF_{4 (g)} ΔH = minus 680. kJ/mol

(Equation 3) 2 C_(s) + 2 H_{2 (g)} arrow C₂H_4(g) ΔH = 52.3 kJ/mol

(Equation 4) C₂H_4(g) + 6 F_2(g) arrow 2 CF_4(g) + 4 HF_(g) ΔH = ???????

To find ΔH for equation 4 you must:

Consider the problem below:

(Equation 1) H_2(g) + F_{2 (g)} ---> 2 HF_(g) ΔH = -542.2 kJ/mol

(Equation 2) 2 H_2(g) + O_2(g)---> 2 H₂O_(l) ΔH = -571.6 kJ/mol

(Equation 3) 2 F_{2 (g)} + 2 H₂O_(l) ---> 4 HF_(g) + O_{2 (g)} ΔH = ???????

To find ΔH for equation 3 you must:

Screen Reader Version

Consider the problem below:

(Equation 1) H_2(g) + F_{2 (g)} arrow 2 HF_(g) ΔH = minus 542.2 kJ/mol

(Equation 2) 2 H_2(g) + O_{2(g) arrow} 2 H₂O_(l) ΔH = minus 571.6 kJ/mol

(Equation 3) 2 F_{2 (g)} + 2 H₂O_(l) arrow 4 HF_(g) + O_{2 (g)} ΔH = ???????

To find ΔH for equation 3 you must:

Consider the problem below:

(Equation 1) 2 HF_(g) ---> H_2(g) + F_{2 (g)} ΔH = 537 kJ/mol

(Equation 2) C_(s) + 2 F_{2 (g)} ---> CF_{4 (g)} ΔH = -680. kJ/mol

(Equation 3) 2 C_(s) + 2 H_{2 (g)} ---> C₂H_4(g) ΔH = 52.3 kJ/mol

(Equation 4) C₂H_4(g) + 6 F_2(g) ---> 2 CF_4(g) + 4 HF_(g) ΔH = ???????

The ΔH for equation 4 is:______(express in kJ)

Screen Reader Version

Consider the problem below:

(Equation 1) 2 HF_(g) arrow H_2(g) + F_2(g) ΔH = 537 kJ/mol

(Equation 2) C_(s) + 2 F_2(g) arrow CF_4(g) ΔH = minus 680. kJ/mol

(Equation 3) 2 C_(s) + 2 H_2(g) arrow C₂H_4(g) ΔH = 52.3 kJ/mol

(Equation 4) C₂H_4(g) + 6 F_2(g) arrow 2 CF_4(g) + 4 HF_(g) ΔH = ???????

The ΔH for equation 4 is:______(express in kJ)

Consider the problem below:

(Equation 1) 2 H₂O_(l) ---> 2 H_2(g) + O_{2 (g)} ΔH = 571.6 kJ

(Equation 2) N₂O_5(g) + H₂O_(l) ---> 2 HNO_3(l) ΔH = -73.7 kJ

(Equation 3) 2 H_2(g) + 6 O_{2 (g)} + 2 N_2(g) ---> 4 HNO_3(l) ΔH = -696.4 kJ

(Equation 4) 2 N_{2 (g)} + 5 O_2(g) ---> 2 N₂O_5(g) ΔH = ???????

The ΔH for equation 4 is:______(express in kJ)

Screen Reader Version

Consider the problem below:

(Equation 1) 2 H₂O_(l) arrow 2 H_2(g) + O_2(g) ΔH = 571.6 kJ

(Equation 2) N₂O_5(g) + H₂O_(l) arrow 2 HNO_3(l) ΔH = minus 73.7 kJ

(Equation 3) 2 H_2(g) + 6 O_2(g) + 2 N_2(g) arrow 4 HNO_3(l) ΔH = minus 696.4 kJ

(Equation 4) 2 N_2(g) + 5 O_2(g) arrow 2 N₂O_5(g) ΔH = ???????

The ΔH for equation 4 is:______(express in kJ)