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The heats of formation (Delta Hf^@) of t...

The heats of formation `(Delta H_f^@)` of the oxides of the third period, sodium to chlorine, are in kJ `"mol"^(-1)`

Based on these data, answer the following questions
Which oxide has maximum negative heat of formation per oxygen atom?

A

`P_4O_10`

B

`Al_2O_3`

C

`Na_2O`

D

`MgO`

Text Solution

Verified by Experts

The correct Answer is:
D
`MgO`
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Knowledge Check

  • The heats of formation (Delta H_f^@) of the oxides of the third period, sodium to chlorine, are in kJ "mol"^(-1) Based on these data, answer the following questions Most stable and least stable oxides are

    A
    `P_4O_10, Cl_2O_7`
    B
    `Na_2O, Cl_2O_7`
    C
    `MgO, Cl_2O_7`
    D
    `Cl_2O_7, MgO`

  • Which of the following equations correctly represents the standard heat of formation (Delta H_(f) ^(@)) of methane?

    A
    `C _(("diamond")) + 2 H _(2) to CH _(4 (g))`
    B
    `C _(("graphite ")) + 2 H _(2(g)) to CH _(4 )`
    C
    `C _(("graphite ")) + 2 H _(2(g)) to CH _(4 (g))`
    D
    `C _(("graphite ")) + 2 4h to CH_(4 (g))`

  • The formation of the oxide ion O^(2-) (g) requires first an exothermic and then an endothermic step as shown below, O(g)+ e^(-) = O^(-)(g), DeltaH^(@)= -142kJmol^(-1) O^(-)(g) +e^(-) =O^(2-)(g), DeltaH^(@)= 844 kJmol^(-1) This is because : oxygen is more electronegative, oxygen has high electron affinity, O^(-) ion will tend to resist the addition of another electron , O^(-) ion has comparatively larger size than oxygen atom

    A
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    B
    oxygen has high electron affinity
    C
    `O^(-)` ion will tend to resist the addition of another electron
    D
    ` O^(-)` ion has comparatively larger size than oxygen atom

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