Reaction of a non-metal with alkali to produce hydrogen gas
This is the extension of Alaska Ron's answer. All reactions taken from this site.

Group 13 elements

All group 13 elements except indium and thallium reacts with aqueous alkali to produce a alkali salt and hydrogen. I'm taking the example of aluminium.

$$\ce{2Al + 2NaOH + 6H2O → 2Na[Al(OH)4] + 3H2}$$

$$\ce{2Al + 2(NaOH•H2O) -&gt;[400-500°C] 2NaAlO2 + 3H2}$$

$$\ce{2Al + 6NaOH -&gt;[450°C] 2NaAlO2 + 3H2 + 2Na2O}$$

$$\ce{2Al + 6H2O + 6NaOH → 2Na3[Al(OH)6] + 3H2}$$

Group 14 elements

Silicon react with sodium hydroxide to produce sodium orthosilicate and hydrogen.

$$\ce{Si + 4NaOH → Na4SiO4 + 2H2}$$

Sodium hydroxide react with silicon and water to produce sodium silicate and hydrogen.

$$\ce{2NaOH + Si + H2O → Na2SiO3 + 2H2}$$

Tin and lead however forms a different product but eventually gives hydrogen gas. Lead only gives the first reaction.

$$\ce{Sn + NaOH + 2H2O → Na[Sn(OH)3] + H2}$$

$$\ce{Sn + 2NaOH + 2H2O → Na2[Sn(OH)4] + H2}$$

$$\ce{Sn + 2NaOH + 4H2O -&gt;[\Delta] Na2[Sn(OH)6] + 2H2}$$

Group 15 elements

Arsenic react with sodium hydroxide to produce sodium orthoarsenate and hydrogen.

$$\ce{As + 3NaOH -&gt;[\Delta] Na3AsO3 + H2}$$