Deck 7: Energy and Chemistry

Question 1

One newton-meter is a unit used to measure both work and energy, it is also equal to one joule.

Answer 1

True

Question 2

Given the thermochemical equation.
N₂(g) + 3H₂(g) → 2NH₃(g) ΔH = −91.8 kJ
91.8 kJ of energy is given off when one mole of N₂ reacts.

Answer 2

True

Question 3

If the ΔH for N₂ + O₂ → 2NO is +180 kJ, for ten moles of NO produced the ΔH is 1,800 kJ.

Answer 3

False

Question 4

If a chemical reaction is reversed, the sign on ΔH is changed.

Question 5

The process of measuring changes in enthalpy is called thermometry.

Question 6

Given the thermochemical equation
N₂(g) + O₂(g) → 2NO(g) ΔH = +180.6 kJ
180.6 kJ of energy is released when two moles of NO are produced.

Question 7

For a given object, the amount of heat is inversely proportional to the mass of the object.

Question 8

The amount of work done by a gas when expanding can be determined by multiplying the final volume and external pressure.

Question 9

Given the thermochemical equation.
N₂(g) + O₂(g) → 2NO(g) ΔH = +180.6 kJ
If 7.00g of N₂ will be reacted, 45.2 kJ will be added. (Molar masses: N = 14 g; O = 16 g)

Question 10

Given the thermochemical equation.
2H₂(g) + O₂(g) → 2H₂O $\Delta$ H = -566 kJ
This equation shows that two moles of hydrogen is needed to produce two moles of H₂O.

Question 11

The heat involved when 150.0 g of Fe increases its temperature from 300.°C to 350.°C is 3370 J. The specific heat of Fe is 0.449 J/g·°C.

Question 12

A chemical equation that includes an enthalpy change is called a thermochemical equation.

Question 13

A chemical reaction that has a positive ΔH is an endothermic reaction.

Question 14

Enthalpy change refers to the pressure of a container when a heat change takes place.

Question 15

An isolated system is a system that does not allow a transfer of energy or matter into or out of the system.

Question 16

The total energy of an isolated system increases when it is internally heated or cooled.

Question 17

Hess's law states that when chemical equations are combined algebraically, their enthalpies can be combined in exactly the same way.

Question 18

The work performed by a gas is 507 J when it expands from 56.3 L to 58.8 L against an external pressure of 2.0 atm.

Question 19

Given the thermochemical equation.
2C(s) + 2O₂(g) → 2CO₂(g) ΔH = −393.50 kJ
The ΔH for the reaction CO₂ → C + O₂ is +196.75 kJ.

Question 20

One calorie is equal to 4.184 kJ.

Question 21

_____ is the transfer of energy from one body to another due to a difference in temperature.

A) Flux
B) Enthalpy
C) Magnetism
D) Entropy
E) Heat

Question 22

Identify the joule equivalent of 4,184 calories.

A) 22,020 J
B) 33,120 J
C) 15,120 J
D) 17,510 J
E) 11,230 J

Question 23

It takes 460.0 J of heat to raise the temperature of 50.00 g of oxygen by 10.00°C. What is the specific heat of O₂ in J/g·°C?

A) 1.935
B) 2.690
C) 0.9200
D) 4.625
E) 1.916

Question 24

What is the work performed when a gas expands from 56.00 mL to 83.00 mL against an external pressure of 760.0 torr? Express the final answer in joules.

A) -10.52 J
B) -20.52 J
C) -3.900 J
D) - 2.736 J
E) -8.900 J

Question 25

The change in enthalpy equals heat at _____.

A) absolute temperature
B) constant pressure
C) consistent volume
D) constant length
E) constant mass

Question 26

CO₂(g) + 2H₂O(l) → CH₄(g) + 2O₂(g). This is an example of a formation reaction in the standard state.

Question 27

The work done by a gas when it expands from 90.0 L to 130.0 L is 2.03 kJ. What is the external pressure acting on the gas?

A) 1.09 *10² atm
B) 5.08 *10¹ pa
C) 3.10 torr
D) 2.01 *10³ atm
E) 2.04 pa

Question 28

In the equation, q = mc $\Delta$ T, the constant 'c' is called _____.

A) entropy
B) atomic radius
C) specific heat capacity
D) electronegativity
E) enthalpy

Question 29

Na + ½ Cl₂ → NaCl. This equation is an example of a formation reaction in the standard state.

Question 30

What is the calorie equivalent of 562.0 J?

A) 346.0 cal
B) 134.0 cal
C) 366.0 cal
D) 155.0 cal
E) 138.0 cal

Question 31

What is the kilojoule equivalent of 54 cal?

A) 5.4 * 10⁵ kJ
B) 2.3 * 10⁶ kJ
C) 2.3 *10^-1 kJ
D) 2.3 * 10^-5 kJ
E) 5.4 * 10^-3 kJ

Question 32

What is the heat involved when 70.0 g of Ag increases its temperature from 90.0°C to 140.0°C? The specific heat of Ag is 0.233 J/g·°C.

A) 583 J
B) 105 J
C) 1,050 J
D) 816 J
E) 1,630 J

Question 33

The heat involved is 208.5 J when 30.0 g of Hg increases its temperature from _____ to 373°C. The specific heat of Hg is 0.139 J/g·°C.

A) 353°C
B) 175°C
C) 50.0°C
D) 315°C
E) 323°C

Question 34

The enthalpy change of any chemical reaction is equal to the sum of the enthalpies of formation of the products minus the sum of the enthalpies of formation of the reactants.

Question 35

What is the SI unit of energy?

A) joule
B) watt
C) ohm
D) newton
E) ampere

Question 36

Given the thermochemical equation.
N₂+ 2O₂ → 2NO₂ ∆H = -114.1 kJ
The enthalpy of formation of NO ₂ is -114.1 kJ.

Question 37

What is the work performed by a gas, if it expands from 5.00 L to 15.0 L against a constant external pressure of 1.62 atm? Express the final answer in joules.

A) -1,640 J
B) -3,280 J
C) -1,230 J
D) -2,460 J
E) -1,850 J

Question 38

A mass of gold increases its temperature from 1.00 x10²°C to 180.°C to produce 309.6 J heat. What mass of Au was present if the specific heat of Au is 0.129 J/g·°C.

A) 10.0 g
B) 15.0 g
C) 30.0 g
D) 45.0 g
E) 60.0 g

Question 39

The work done by a gas when it expands to 96 L is 4,100 J. If the external pressure is 2.0 atm, determine the initial volume of the gas.

A) 56 L
B) 16 L
C) 20 L
D) 36 L
E) 76 L

Question 40

The enthalpy of formation of O₂ is 0 kJ.

Question 41

To warm 800.0 g of H₂O, 0.025 mol of phenol (C₆H₅OH) is burned. The water warms from 24.6 $\degree$ C to 65.6 $\degree$ C. What is the ΔH of the reaction on a molar basis?

A) 4,110 kJ
B) 5,480 kJ
C) 1,600 kJ
D) 2,740 kJ
E) 1,370 kJ

Question 42

Which of the following thermochemical equations is used to represent the reaction of H₂(g) with O₂(g) to make H₂O(ℓ) giving off 572 kJ?

A) H₂(g) + O₂(g) $\rightarrow$ H₂O(ℓ) ; $\Delta$ H = −572 kJ
B) H₂(g) + O₂(g) $\rightarrow$ 2H₂O(ℓ) ; $\Delta$ H = +572 kJ
C) H₂(g) + O₂(g) $\rightarrow$ 2H₂O(ℓ) ; $\Delta$ H = −286 kJ
D) 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(ℓ) ; $\Delta$ H = −572 kJ
E) 2H₂(g) + 2O₂(g) $\rightarrow$ 4H₂O(ℓ) ; $\Delta$ H = −286 kJ

Question 43

Consider the reaction: NH₃ + HCl → NH₄Cl ΔH = -176.0 kJ
How much energy is given off when 170.3 g of NH₄Cl is formed? (Molar mass of NH₄Cl = 53.49 g/mol)

A) 713.4 kJ
B) 153.4 kJ
C) 230.2 kJ
D) 560.3 kJ
E) 1,274 kJ

Question 44

Given the thermochemical equations, Ni + Cl₂ → NiCl₂ ΔH = −383 kJ
NiCl₂ + Cl₂ → NiCl₄ ΔH = −192 kJ
What is the ΔH for 2NiCl₂ → Ni + NiCl₄?

A) +191 kJ
B) +575 kJ
C) -191 kJ
D) +383 kJ
E) -575 kJ

Question 45

Consider the thermochemical equation 2C₂H₆(g) + 7O₂(g) → 4CO₂(g) + 6H₂O(ℓ); ΔH = -3,120 kJ
What amount of oxygen can consume 6,240 kJ of energy? (Molar masses: C₂H₆ = 30.0 g; O₂ = 32.0 g)?

A) 6.40 *10² g
B) 1.28 * 10² g
C) 2.24 *10² g
D) 3.20 *10² g
E) 4.48 * 10² g

Question 46

Calorimetry is the process of measuring _____ changes.

A) enthalpy
B) pressure
C) density
D) entropy
E) volume

Question 47

Consider the thermochemical equation N₂(g) + O₂(g) → 2NO(g) ΔH = +180.6 kJ
If 550 kJ of energy is supplied, determine the mass of nitrogen monoxide reacted. (Molar masses: N =14.00 g; O = 16.00 g)

A) 14.0 g
B) 28.0 g
C) 84 g
D) 182.7 g
E) 180 g

Question 48

A chemical equation that includes an enthalpy change is called a(n) _____.

A) ionic equation
B) hydro equation
C) radioactive equation
D) thermochemical equation
E) electrochemical equation

Question 49

Consider the thermochemical equation: 2C₂H₆(g) + 7O₂(g) → 4CO₂(g) + 6H₂O(ℓ); ΔH = -3,120 kJ
How much energy is given off when 45.0 g of C₂H₆ and 96.0 g of oxygen are reacted? (Molar masses: C₂H₆ = 30.0 g; O₂ = 32.0 g)

A) 1,340 kJ
B) 3,120 kJ
C) 1,560 kJ
D) 782 kJ
E) 2,670 kJ

Question 50

_____ refers to the heat of a process when pressure is held constant.

A) Exothermic transformation
B) Entropy change
C) Specific heat
D) Radiation
E) Enthalpy change

Question 51

For 2Na + Cl₂ → 2NaCl ΔH is −772 kJ. What is the ΔH for the reaction NaCl → Na + ½Cl₂?

A) +386 kJ
B) −772 kJ
C) −386 kJ
D) +772 kJ
E) −579 kJ

Question 52

How much energy is given off or absorbed when 26.0 mol of O₂ is reacted? CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(ℓ) ΔH = −890 kJ

A) 28,900 kJ is absorbed
B) 34,700 kJ is given off
C) 5,790 kJ is absorbed
D) 23,100 kJ is given off
E) 11,600 kJ is given off

Question 53

Consider this thermochemical equation: CO₂(g) + H₂(g) $\rightarrow$ CO(g) + H₂O(g) ΔH = 42 kJ
How much energy is given off or absorbed when 22 g of CO₂ is reacted?

A) 42 kJ is absorbed
B) 42 kJ is given off
C) 21 kJ is given off
D) 21 kJ is absorbed
E) 22 kJ is absorbed

Question 54

Which of the following is a container used to measure the heat of a chemical reaction?

A) manometer
B) calorimeter
C) barometer
D) altimeter
E) accelerometer

Question 55

_____ law states that when chemical equations are combined algebraically, their enthalpies can be combined in exactly the same way.

A) Avogadro's
B) Henry's
C) Charles's
D) Boyle's
E) Hess's

Question 56

Consider the thermochemical equation: N₂ + O₂ → 2NO; ΔH = +180.6 kJ
How many moles of nitrogen should be reacted to absorb 6.00 *10² kJ of energy?

A) 2.77 mol
B) 4.93 mol
C) 3.32 mol
D) 7.40 mol
E) 14.8 mol

Question 57

A solution of 0.100 mol of Ca²⁺ was mixed with 0.200 mol Cl^- ions and CaCl₂ was precipitated: Ca²⁺ + 2Cl^-→ CaCl₂
The temperature of the solution is increased by 21.00°C. What was the mass of the solution reacted if the enthalpy change for the production of 1 mol of CaCl₂ is 176.0 kJ? (Assume that the solution has the same specific heat as water)?

A) 11.00 g
B) 100.0 g
C) 150.0 g
D) 200.0 g
E) 250.0 g

Question 58

Given the thermochemical equation 2C(s) + 2O₂(g) → 2CO₂(g) ΔH = −787 kJ
What is the ΔH for the reaction CO₂(g) → C(s) + O₂(g)?

A) −0.00250 kJ
B) −394 kJ
C) +0.00250 kJ
D) +394 kJ
E) −787 kJ

Question 59

Given the thermochemical equations, B₂O₃(s) + 3H₂O(g) → 3O₂(g) + B₂H₆(g) ΔH = −2,035 kJ
H₂O(ℓ) → H₂O(g) ΔH = 44 kJ
H₂ (g) + ½O₂(g) → H₂O(ℓ) ΔH = −286 kJ
2B(s) + 3H₂(g) → B₂H₆(g) ΔH = 36 kJ
What is the ΔH_f for 4B(s) + 3O₂(g) → 2B₂O₃(s)?

A) +1,273 kJ
B) +2,690 kJ
C) -1,273 kJ
D) -5,594 kJ
E) +636.5 kJ

Question 60

Given the following thermochemical equation 2SO₂ + O₂→2SO₃ ΔH = -395.2 kJ
If 5,455 kJ is given off for the formation of SO₃, what quantity of O₂ in moles is reacted?

A) 15.22 mol
B) 4.180 mol
C) 3.135 mol
D) 13.80 mol
E) 10.45 mol

Question 61

Consider the equation. N₂(g)+ O₂(g)→ 2NO(g) ∆H = 180.6 kJ
What is the enthalpy of formation for NO?

A) 90.3 kJ
B) 66.2 kJ
C) 99.3 kJ
D) 49.4 kJ
E) 132.4 kJ

Question 62

If the ΔH for C₃H₆ + H₂ → C₃H₈ is −125 kJ, what is the ΔH for the reaction 2C₃H₈ →2C₃H₆ + 2H₂?

A) +250 kJ
B) +125 kJ
C) +62.5 kJ
D) −125 kJ
E) −250 kJ

Question 63

What will be the coefficient of Cl₂ when the following equation is written as a proper formation reaction? H₂ + Cl₂ → 2HCl

A) 1/4
B) 1/2
C) 1
D) 2
E) 4

Question 64

Identify the product that has zero enthalpy of formation.

A) NO
B) NO₂
C) NH₃
D) O₂
E) O₃

Question 65

Write the equivalences of the equation H₂(g) + Cl₂(g) → 2HCl(g) ΔH = −184.6 kJ.

Question 66

What is energy? What are its units?

Question 67

Explain the relationship between external pressure and the work done by gases when expanding.

Question 68

What is specific heat capacity.

Question 69

Given the equations A + 6B → 4E ΔH = −234 kJ
2B +4C → 2E ΔH = −100 kJ
What is the ΔH for the reaction A + 2B → 8C?

A) +34 kJ
B) −34 kJ
C) +134 kJ
D) +434 kJ
E) −434 kJ

Question 70

Explain the concept of Hess's law.

Question 71

Which of the following is an example of a proper formation reaction?

A) 2Na(s) + Cl₂(g) → 2NaCl(s)
B) 2H₂(g) + O₂(g) → 2H₂O(ℓ)
C) Ca(s) + C(s) + 3/2 O₂(g) → CaCO₃(s)
D) 2Fe(s) + 3P(s) + 12O(g) → Fe₂(PO₄)₃
E) H₂(g) + Cl₂(g) → 2HCl

Question 72

What are exothermic and endothermic reactions?

Question 73

Given the unbalanced reaction and the enthalpies of formation of molecules. H₂SO₄ (ΔH_f = −814.00 kJ/mol) + NaCl (ΔH_f = −385.90 kJ/mol) → Na₂SO₄ (ΔH_f = −331.64 kJ/mol) + HCl (ΔH_f = −92.31 kJ/mol)
What is the enthalpy change of the reaction?

A) −2,670.80 kJ
B) +1,069.54 kJ
C) +2,670.80 kJ
D) −852.35 kJ
E) +1,898.49 kJ

Question 74

The enthalpy of formation for C₂H₅OH is −277.0 kJ. What is the ∆H for the following reaction? 4C(s) + 6H₂(g) + 2O₂(g)→ 2C₂H₅OH(ℓ)

A) +277.0 kJ
B) −277.0 kJ
C) −554.0 kJ
D) +831.0 kJ
E) +544.0 kJ

Question 75

Enthalpy change of any chemical reaction = _____

A) sum of the enthalpies of formation of the products + sum of the enthalpies of formation of the reactants
B) 2(sum of the enthalpies of formation of the reactants) + 2(sum of the enthalpies of formation of the products)
C) sum of the enthalpies of formation of the products × sum of the enthalpies of formation of the reactants
D) sum of the enthalpies of formation of the products − sum of the enthalpies of formation of the reactants
E) sum of the enthalpies of formation of the products ÷ sum of the enthalpies of formation of the reactants

Question 76

What is heat? How is it related to the temperature change and the mass of the object? What instrument is used to measure heat?

Question 77

Describe systems and isolated systems. Provide examples.

Question 78

How are ΔH values measured experimentally?

Question 79

What is enthalpy change? What is a thermochemical equation?

Question 80

_____ reactions are chemical reactions that produce one mole of a substance from its constituent elements in their standard states.

A) Formation
B) Reduction
C) Hydration
D) Oxidation
E) Combustion