Write equation for the following chemical reaction, including state symbols.

Zinc metal reacts with hydrochloric acid to form the salt zinc chloride. Hydrogen gas is evolved.

Write equation for the following chemical reaction, including state symbols.

Hydrogen gas and oxygen gas react together to form water. 

Write equation for the following chemical reaction, including state symbols.

At a high temperature, calcium carbonate decomposes into calcium oxide and carbon dioxide. 

Deduce the percentage atom economy for the nucleophilic substitution reaction:

${\mathrm{CH}}_3{\left({\mathrm{CH}}_2\right)}_3\mathrm{OH}+\mathrm{NaBr}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{CH}}_3{\left({\mathrm{CH}}_2\right)}_3\mathrm{Br} +{\mathrm{H}}_2\mathrm{O}+{\mathrm{NaHSO}}_4$

Identify the type of reaction and then copy and balance the equation, using the smallest possible whole number coefficients. 

${\mathrm{SO}}_3\left(\mathrm{g}\right) + {\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \to {\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)$ 

Identify the type of reaction and then copy and balance the equation, using the smallest possible whole number coefficients.

${\mathrm{NCI}}_3\left(\mathrm{g}\right) \to {\mathrm{N}}_2\left(\mathrm{g}\right) + {\mathrm{Cl}}_2\left(\mathrm{g}\right)$

Identify the type of reaction and then copy and balance the equation, using the smallest possible whole number coefficients.

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