Topic 5/15 and 6/16 Review

Topic 5/15 and 6/16 Review

• H=q/n

Open Ended

3.26 g of iron powder are added to 80.0 cm3 of 0.200 mol dm−3 copper(II) sulfate solution. The following reaction occurs:

Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)

The reaction was carried out in a calorimeter. The maximum temperature rise of the solution was 7.5 °C.

The enthalpy change was calculated from this data using q=mcΔT.

State two assumptions made in the enthalpy change calculation.

all heat was absorbed by the solution

OR

density «of solution» is 1.00 g cm−3

OR

specific heat capacity «of solution» is 4.18 J g−1 K−1/that of «pure» water

OR

reaction goes to completion

OR

iron/CuSO4 does not react with other substances ✔

Multiple Choice

Consider the following reactions:

Fe₂O₃ (s) + CO (g) → 2FeO (s) + CO₂ (g) ΔH^Θ = −3 kJ

Fe (s) + CO₂ (g) → FeO (s) + CO (g) ΔH^Θ = +11 kJ

What is the ΔH^Θ value, in kJ, for the following reaction?

Fe₂O₃ (s) + 3CO (g) → 2Fe (s) + 3CO₂ (g)

• −25

• −14

• +8

• +19

Multiple Choice

What is the enthalpy change of the reaction?

C₆H₁₄ (l) → C₂H₄ (g) + C₄H₁₀ (g)

• + 1411 + 2878 + 4163

• + 1411 − 2878 − 4163

• + 1411 + 2878 − 4163

• − 1411 − 2878 + 4163

Multiple Choice

Which statement is correct?

• O₃ bond dissociation occurs at a longer wavelength of light than O₂ bond dissociation.

• O₃ bond dissociation occurs at a higher energy than O₂ bond dissociation.

• O₃ bond lengths are shorter than O₂ bond lengths

• O₃ bond dissociation occurs at a higher frequency of light than O₂ bond dissociation.

Multiple Choice

Consider the reaction and data.

Which calculation gives ΔH^Θ, in kJ, for the forward reaction?

• 2z − y − 3x

• y + 3x − 2z

• y + 3x − 6z

• 6z − y − 3x

Open Ended

Ethyne can be converted to benzene. The ΔH^Θ values for the reaction was calculated under two different scenarios:

(i) 3C₂H₂(g) → C₆H₆(g) using bond enthalpy values

(ii) 3C₂H₂(g) → C₆H₆(l) using enthalpy of formation values

The results were (i) 475 kJ and (ii) 600 kJ.

Explain, giving two reasons, the difference in the values from (i) and (ii).

ΔHf values are specific to the compound

OR

bond enthalpy values are averages «from many different compounds»

 

condensation from gas to liquid is exothermic

 

Accept “benzene is in two different states «one liquid the other gas»” for M2.

Multiple Select

Which statements are correct for ionic compounds?

• Lattice energy increases as ionic radii increase.

• Within the same group, the melting point of salts tends to decrease as the radius of the cation increases.

• Solubility in water depends on the relative magnitude of the lattice energy compared to the hydration energy.

Multiple Choice

Which combination gives the standard hydration enthalpy of Na⁺(g)

• 4 + 359 + 790

• 4 + 359 − 790

• − 4 − 359 + 790

• 4 − 359 + 790

Multiple Choice

Which reaction becomes more spontaneous as temperature increases?

• A

• B

• C

• D

G = H − TS

Multiple Choice

What is the order with respect to each reactant?

• NO = 0 Cl2 = 1

• NO = 1 Cl2 = 1

• NO = 2 Cl2 = 1

• NO = 2 Cl2 = 2

Multiple Choice

Which is correct?

• A

• B

• C

• D

Multiple Choice

What is the effect of increasing temperature on the rate constant, k?

• The rate constant does not change.

• The rate constant decreases linearly.

• The rate constant increases exponentially.

• The rate constant increases proportionally with temperature.

Multiple Choice

What is the activation energy of the reverse reaction?

• A

• B

• C

• D