Sergey Bylikin, Gary Horner and, Brian Murphy Solutions for Chapter: Energetics and Thermochemistry (AHL), Exercise 3: Quick questions

Predict whether the following reactions will have a positive or negative entropy change, $∆{\mathrm{S}}^{⊝}$.

${\mathrm{NH}}_4{\mathrm{NO}}_3\left(\mathrm{s}\right) \to {\mathrm{N}}_2\mathrm{O}\left(\mathrm{g}\right) + 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Give answer as either positive or negative.

Predict whether the following reactions will have a positive or negative entropy change, $∆{\mathrm{S}}^{⊝}$.

${\mathrm{N}}_2\left(\mathrm{g}\right) + 3{\mathrm{H}}_2\left(\mathrm{g}\right) \to 2{\mathrm{NH}}_3 \left(\mathrm{g}\right)$

Give answer as either positive or negative.

Predict whether the following reactions will have a positive or negative entropy change, $∆{\mathrm{S}}^{⊝}$.

${\mathrm{N}}_2{\mathrm{O}}_4\left(\mathrm{g}\right) \to 2{\mathrm{NO}}_2 \left(\mathrm{g}\right)$

Give answer as either positive or negative.

Predict whether the following reactions will have a positive or negative entropy change, $∆{\mathrm{S}}^{⊝}$.

${\mathrm{CaCO}}_3 \left(\mathrm{s}\right) \to \mathrm{CaO}\left(\mathrm{s}\right) + {\mathrm{CO}}_2\left(\mathrm{g}\right)$

Give answer as either positive or negative.

Predict whether the following reactions will have a positive or negative entropy change, $∆{\mathrm{S}}^{⊝}$.

$2{\mathrm{C}}_2{\mathrm{H}}_6 \left(\mathrm{g}\right) +7{\mathrm{O}}_2 \left(\mathrm{g}\right) \to 4{\mathrm{CO}}_2 \left(\mathrm{g}\right) + 6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Give answer as either positive or negative.

The equation for the reaction between carbon dioxide and hydrogen is shown below.

${\mathrm{CO}}_2 \left(\mathrm{g}\right) + 4{\mathrm{H}}_2 \left(\mathrm{g}\right) \to {\mathrm{CH}}_4\left(\mathrm{g}\right) + 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

The table shows the standard entropy values of the substances in the reaction above.

Calculate the standard entropy change for the reaction. Explain how the sign can be predicted from the equation for the reaction.