Word equation – write balanced molecular equation:
$A)$ Sodium $+$ oxygen $\to$ sodium oxide
$B)$ Calcium $+$ water $ \to $ calcium hydroxide $ + $hydrogen
$C)$ Zinc $ + $ oxygen $ \to $ zinc oxide
$D)$ Carbon monoxide $ + $ oxygen $ \to $ carbon dioxide
$E)$ Potassium oxide $ + $ water $ \to $ potassium hydroxide
$F)$ Magnesium $ + $ carbon dioxide $ \to $ magnesium hydroxide $ + $ carbon
$G)$ Potassium $ + $ water $ \to $ potassium hydroxide $ + $ hydrogen
$H)$ Calcium chloride $ + $ sodium carbonate $ \to $ sodium chloride $ + $ calcium carbonate
$I)$ Zinc$ + $ dil. Hydrochloric acid $ \to $ zinc chloride $ + $ hydrogen
$J)$ Zinc$ + $ sodium hydroxide $ \to $ sodium zincate $ + $ hydrogen
$K)$ Zinc sulphate $ + $ sodium hydroxide $ \to $ sodium sulphate $ + $ zinc hydroxide

Hint: Each element is represented by a different symbol. All these symbols are in the periodic table.
We can use these symbols to show molecules of compounds, and they can show us the ratio of the different elements which combine to form compounds.

Complete answer:
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus and minus signs.
There are three which we have to follow while writing molecular equations from the word equation.
Identify reactants and products and place them in a word equation.
Convert the chemical names into chemical formulas. Place them based on the chemical equation and write the state symbols.
Balance the chemical equation
When compounds react, they are chemically changed into new compounds. Every chemical change can be communicated symbolically using a chemical equation. Chemical equations combine formulas with other symbols to show what changes take place.
$A)$ Sodium $+$ oxygen $ \to $ sodium oxide
$4Na + {O_2} \to N{a_2}O$
$B)$ Calcium $ + $ water $ \to $ calcium hydroxide $ + $ hydrogen
$Ca + 2{H_2}O \to Ca{(OH)_2} + {H_2}$
$C)$Zinc $ + $ oxygen $ \to $ zinc oxide
$Zn + {O_2} \to ZnO$
$D)$ Carbon monoxide $ + $ oxygen $ \to $ carbon dioxide
$CO + O \to C{O_2}$
$E)$ Potassium oxide $ + $ water $ \to $ potassium hydroxide
${K_2}O + {H_2}O \to 2KOH$
$F)$ Magnesium $ + $ carbon dioxide $ \to $ magnesium hydroxide $ + $ carbon
$Mg + C{O_2} \to 2MgO + C$
$G)$ Potassium $ + $ water $ \to $ potassium hydroxide $ + $ hydrogen
$2K + 2{H_2}O \to 2KOH + {H_2}$
$H)$ Calcium chloride $ + $ sodium carbonate $ \to $ sodium chloride $ + $ calcium carbonate
\[N{a_2}C{O_3} + \;CaC{l_2} \to CaC{O_3} + {\text{ }}2{\text{ }}NaCl{\text{ }}\;\]
$I)$ Zinc $ + $ dil. Hydrochloric acid $ \to $ zinc chloride $ + $ hydrogen
\[Zn\; + \;HCl \to {\text{ZnC}}{{\text{l}}_2}\; + {\text{ }}{H_2}\mathbb{S}\]
$J)$ Zinc $ + $ sodium hydroxide $ \to $ sodium zincate $ + $ hydrogen
\[Zn + \;NaOH\; \to {\text{ }}N{a_2}Zn{O_2} + {\text{ }}{H_2}\]
$K)$ Zinc sulphate $ + $ sodium hydroxide $ \to $ sodium sulphate $ + $ zinc hydroxide
\[NaOH\; + \;ZnS{O_4}\; \to \;N{a_2}S{O_4} + \;Zn{(OH)_2}\]

Note:
Chemical equations should be balanced on the basis of law of conservation of mass, i.e. number of atoms of the elements on the left side should be equal to the number of atoms of the same elements on the right side. The reactants and products are separated by an arrow, usually read aloud as yields.