Chapter 9, Problem 121A

Predict When sodium metal reacts with water, it produces sodium hydroxide, hydrogen gas, and heat. Write balanced chemical equations for reacting with water. Use Figure 9.13 to predict the order of the amount ofheat released from least to most amount of heat released.

Interpretation Introduction

Interpretation:

The balanced chemical equations for reaction of Li, Na and K with water needs to be determined. The order of the amount of heat released from least to most needs to be determined.

Concept introduction:

The reactivity series of metals is as follows:

Lithium > Rubidium > Potassium > Calcium > Sodium > Magnesium > Aluminium > Manganese > Zinc > Iron > Nickel > Tin > Lead > Copper > Silver > Platinum > Gold

Answer to Problem 121A

Lithium reaction releases maximum amount of heat which is followed by the potassium reaction and lastly by the sodium reaction.

Following are the complete balanced reactions:

$\text{Li}\left(\text{s}\right)\text{+}{\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{LiOH}\left(\text{aq}\right)$ is the lithium reaction.

$\text{K}\left(\text{s}\right)\text{+}{\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{KOH}\left(\text{aq}\right)$ is the potassium reaction.

$\text{Na}\left(\text{s}\right)\text{+}2{\text{H}}^{\text{+}}\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}Na\text{OH}\left(\text{aq}\right)$ is the sodium reaction.

Explanation of Solution

The reactivity series of metals is as follows:

Lithium > Rubidium > Potassium > Calcium > Sodium > Magnesium > Aluminium > Manganese > Zinc > Iron > Nickel > Tin > Lead > Copper > Silver > Platinum > Gold

On the basis of the order of reactivity series of metals we can conclude that Lithium reaction releases maximum amount of heat which is followed by the potassium reaction and lastly by the sodium reaction.

Following are the complete balanced reactions:

$\text{Li}\left(\text{s}\right)\text{+}{\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{LiOH}\left(\text{aq}\right)$ is the lithium reaction.

$\text{K}\left(\text{s}\right)\text{+}{\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{KOH}\left(\text{aq}\right)$ is the potassium reaction.

$\text{Na}\left(\text{s}\right)\text{+}2{\text{H}}^{\text{+}}\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}Na\text{OH}\left(\text{aq}\right)$ is the sodium reaction.

Conclusion

Lithium reaction releases maximum amount of heat which is followed by the potassium reaction and lastly by the sodium reaction. This can be concluded on the basis of reactivity series of metals.

Following are the complete balanced reactions:

$\text{Li}\left(\text{s}\right)\text{+}{\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{LiOH}\left(\text{aq}\right)$ for lithium.

$\text{K}\left(\text{s}\right)\text{+}{\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{KOH}\left(\text{aq}\right)$ for potassium.

$\text{Na}\left(\text{s}\right)\text{+}2{\text{H}}^{\text{+}}\text{+}{\text{OH}}^{\text{-}}\left(\text{aq}\right)\to {\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}\text{NaOH}\left(\text{aq}\right)$ for sodium.