Tag: reaction of metals

$2Al(s) + 3H _2O(g) \rightarrow Al _2O _3(s) + 3H _2(g)$

$2K(s) + 2H _2O(l) \rightarrow $2$KOH$(aq) + $H _2(g)$ + heat energy

Hydrogen gas is formed when magnesium reacts with water to form its hydroxide as Mg is highly reactive with water and acids. It is present on the top of the activity series. So, it is a very reactive metal.

$4Al(s) + 3O _2(g) \rightarrow 2Al _2O _3(s)$

The metals, which are low in the reactive series, undergo reduction reaction. Their metal oxides react with carbon to reduce the metal oxide to its metal and form an oxide of carbon.
$2CuO+C \rightarrow 2Cu+CO _2$

Metals from magnesium to iron in the activity series of metals, react with steam (but not $H _2O$) to form the metal oxide and hydrogen gas.

Metal forms basic oxides which reacts with water and forms base as
$M-2e^- \rightarrow M^{+2}$
$MO+H _2O \rightarrow M(OH) _2$

Magnesium has almost no reaction with cold water. It reacts very slowly with hot water.  It reacts with steam when being heated and gives hydrogen gas and metal oxide.
Magnesium + Water $\rightarrow$  Magnesium hydroxide + Hydrogen gas
Zinc and iron do not react with cold or hot water.  They react with  steam slowly to give the respective oxides:
Zinc + Steam $\rightarrow$  Zinc oxide  + Hydrogen gas
Iron + Steam $\rightarrow$ Iron(II) iron(III) oxide  + Hydrogen gas

The reactivity of active metals can be demonstrated by dropping pieces of $Li, Na, K$ into water. $Li$ reacts slowly with water, $Na$ reacts more rapidly and $K$ reacts violently. For a reaction between sodium and water, it can be divided into two halves. One-half reaction describes what happens when sodium atoms lose electrons. The other half describes what happens when water molecules gain these electrons. An overall equation is obtained for the reaction which shows the formation of metal hydroxide and evolution of hydrogen gas.
$2Na\left( s \right) +2{ H } _{ 2 }O\left( l \right) \rightarrow 2{ Na }^{ + }\left( aq \right) +2{ OH }^{ - }\left( aq \right) +{ H } _{ 2 }\left( g \right) \uparrow $