Explain the following reaction giving their balanced chemical equation.

1. Copper reacts with conc. nitric acid.
2. Magnesium is treated with hydrochloric acid.
3. Aluminium is treated with dil. hydrochloric acid.
4. Copper reacts with dil nitric acid.
5. Sugar is heated.

1. When copper reacts with conc. nitric acid, reddish coloured poisonous nitrogen dioxide gas is formed

.
$\mathrm{Cu}\left(s\right)+4{\mathrm{HNO}}_3\left(\mathrm{aq}\right)\to \mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2{\mathrm{NO}}_2+2H_{2}O\left(l\right)\left(\mathrm{conc}\right)\mathrm{Nitric}\mathrm{dioxide}$
2. When magnesium is treated with hydrochloric acid, hydrogen gas is liberated.

$\mathrm{Mg}\left(s\right)+2\mathrm{HCl}\to {\mathrm{MgCl}}_2+H_2\uparrow \mathrm{Magnesium}\left(\mathrm{dil}.\right)\mathrm{Magnesium}\mathrm{Hydrogen}\mathrm{Chloride}$
3.When aluminium is treated with dilute hydrochloric acid, hydrogen gas is liberated.
$2\mathrm{Al}\left(s\right)+6\mathrm{HCl}\left(\mathrm{aq}\right)\to 2{\mathrm{AlCl}}_3+3H_2\uparrow \mathrm{Aluminium}\mathrm{Aluminium}\mathrm{Hydrogen}\mathrm{chloride}$
4. When copper react with dil. nitric acid, nitric gas is formed.
$Cu\left(s\right)+8HN{O}_3\left(aq\right)\to 3Cu{\left(N{O}_3\right)}_2\left(aq\right)+2NO\left(g\right)+2H_{2}O\left(l\right)(dil.)Nitricoxide$

5. When sugar is heated, it decomposes to form carbon (Black substance)
$C_{12}{H}_{22}{O}_{11}\stackrel{\Delta }{\to }12C+11H_{2}O\left(g\right)SugarCarbon$