Chapter 5 - Thermochemistry SL Review

What energy changes occur when chemical bonds are formed and broken?

• Energy is absorbed when bonds are formed and when they are broken

• Energy is released when bonds are formed and when they are broken

• Energy is absorbed when bonds are formed and released when they are broken

• Energy is released when bonds are formed and absorbed when they are broken

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NGSS.HS-PS1-4

The temperature of a 2.0 g sample of aluminum increases from 25C to 30C. How many joules of heat energy were added? (Specific heat of aluminum = 0.90 J/gK)

• 0.36

• 2.3

• 9.0

• 11

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Using the equations:

C(s) + O₂(g) → CO₂(g) ΔH = -390 kJ

Mn(s) + O₂(g) → MnO₂(s) ΔH = -520 kJ

what is ΔH for the reaction: MnO₂(s) + C(s) → Mn(s) + CO₂(g)?

• 910

• 130

• -130

• -910

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What is ΔH for the reaction below in kJ?

CS₂(g) + 3O₂(g) → CO₂(g) + 2SO₂(g)

(ΔH_f (kJ/mol): CS₂(g) = 110, CO₂(g) = -390, SO₂(g) = 290)

• -570

• -790

• -860

• -1080

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NGSS.HS-PS1-4

Which statements about exothermic reactions are correct?

I. They have negative ΔH values II. The products have a lower enthalpy than the reactants III. The products are more energetically stable than the reactants

• I and II only

• I and III only

• II and III only

• I, II, and III

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A sample of a metal is heated. Which of the following are needed to calculate the heat absorbed by the sample?

I. the mass of the sample II. the density of the sample III. the specific heat capacity of the sample

• I and II only

• I and III only

• II and III only

• I, II, and III

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The average bond enthalpies for O-O and O=O are 146 and 496 kJ/mol respectively. What is the enthalpy change, in kJ, for the reaction below?

H-O-O-H(g) → H-O-H(g) + ½O=O(g)

• -102

• +102

• +350

• +394

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NGSS.HS-PS1-4

What is the energy change (in kJ) when the temperature of 20 g of water increases by 10C?

• 20 x 10 x 4.18

• 2 x 283 x 4.18

• (20 x 10 x 4.18)/1000

• (20 x 283 x 4.18)/1000

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When the solids Ba(OH)₂ and NH₄SCN are mixed, a solution is produced and the temperature drops. Which statement about the energetics of this reaction is correct?

• The reaction is endothermic and ΔH is negative

• The reaction is endothermic and ΔH is positive

• The reaction is exothermic and ΔH is negative

• The reaction is exothermic and ΔH is positive

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NGSS.HS-PS1-4

For which of the following is the sign of the enthalpy change different from the other three?

• CaCO₃(s) → CaO(s) + CO₂(g)

• Na(g) → Na⁺(g) + e^-

• CO₂(s) → CO₂(g)

• 2Cl(g) → Cl₂(g)

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NGSS.HS-PS1-4