Question

Complete and balance the following chemical equations:
(a) $Zn(s)+HCl(aq)\to $
(b) $N{{a}_{2}}C{{O}_{3}}(s)+2HCl(aq)\to $
(c) $NaHC{{O}_{3}}(s)+HCl(aq)\to $
(d) $NaOH(aq)+HCl(aq)\to $
(e) $CuO(s)+HCl(aq)\to $

Answer 1

Hint: The addition of stoichiometric coefficients to the reactant and products involves balancing chemical equations. The law of conservation must be followed by chemical equations and the law of constant proportions is very important in balancing chemical equations. The traditional balancing method and the algebraic balancing method are the two quick easy methods of balancing a chemical equation.

Complete step by step solution:
The arrowhead points show the direction of products in the reaction.
A chemical equation represents a chemical reaction when chemical formulas are used instead of words. Balancing the given chemical equation using traditional balancing method:
Step-1: first complete the given equations with products
(a) $Zn(s)+HCl(aq)\to ZnC{{l}_{2}}(aq)+{{H}_{2}}(g)$
(b) $N{{a}_{2}}C{{O}_{3}}(s)+2HCl(aq)\to NaCl(aq)+{{H}_{2}}O(l)+C{{O}_{2}}(g)$
(c) $NaHC{{O}_{3}}(s)+HCl(aq)\to NaCl(aq)+C{{O}_{2}}(g)+{{H}_{2}}O(l)$
(d) $NaOH(aq)+HCl(aq)\to NaCl(aq)+{{H}_{2}}O(l)$
(e) $CuO(s)+HCl(aq)\to CuC{{l}_{2}}(aq)+{{H}_{2}}O(l)$
Step-2: Count and compare the number of atoms of each element on LHS and RHS of the arrow. Check the number of atoms of each element is the same on both sides of the reaction, then the equation is said to be unbalanced. Because both sides of the chemical equation, the mass is not the same.

(a) Chemical equation: $Zn(s)+HCl(aq)\to ZnC{{l}_{2}}(aq)+{{H}_{2}}(g)$
Reactants side	Product side
One Zn from Zn(s)	One Zn from Zn(s)
One hydrogen atom from HCl(aq)	two hydrogen atoms from ${{H}_{2}}(g)$
One Chlorine atom from HCl (aq)	Two Chlorine atom from $ZnC{{l}_{2}}(aq)$
(b) Chemical equation: $N{{a}_{2}}C{{O}_{3}}(s)+2HCl(aq)\to NaCl(aq)+{{H}_{2}}O(l)+C{{O}_{2}}(g)$
Reactants side	Product side
Two sodium atoms from $N{{a}_{2}}C{{O}_{3}}$	One Na atom from NaCl
One C atom from $N{{a}_{2}}C{{O}_{3}}$	One C atom from $C{{O}_{2}}$
three O atoms from $N{{a}_{2}}C{{O}_{3}}$	one O atom from ${{H}_{2}}O$ and two O atoms from $C{{O}_{2}}$
Two hydrogen atoms from HCl	Two hydrogen atoms from ${{H}_{2}}O$
(c) Chemical equation: $NaHC{{O}_{3}}(s)+HCl(aq)\to NaCl(aq)+C{{O}_{2}}(g)+{{H}_{2}}O(l)$
Reactants side	Product side
one sodium atom from $NaHC{{O}_{3}}$	One Na atom from NaCl
One C atom from $NaHC{{O}_{3}}$	One C atom from $C{{O}_{2}}$
three O atoms from $NaHC{{O}_{3}}$	one O atom from ${{H}_{2}}O$ and two O atoms from $C{{O}_{2}}$
Two hydrogen atoms from HCl and $NaHC{{O}_{3}}$	Two hydrogen atoms from ${{H}_{2}}O$
(d) Chemical equation: $NaOH(aq)+HCl(aq)\to NaCl(aq)+{{H}_{2}}O(l)$
Reactants side	Product side
one sodium atom from NaOH	One Na atom from NaCl
One Cl atom from HCl	One Cl atom from NaCl
One O atom from NaOH	one O atom from ${{H}_{2}}O$
Two hydrogen atoms from HCl and NaOH	Two hydrogen atoms from ${{H}_{2}}O$
(e) Chemical equation: $CuO(s)+HCl(aq)\to CuC{{l}_{2}}(aq)+{{H}_{2}}O(l)$
Reactants side	Product side
one Cu atom from CuO	One Cu atom from $CuC{{l}_{2}}$
One Cl atom from HCl	Two Cl atoms from $CuC{{l}_{2}}$
One O atom from CuO	one O atom from ${{H}_{2}}O$
One hydrogen atom from HCl	Two hydrogen atoms from ${{H}_{2}}O$

Step: 3 Recollect once, the law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction, which means the total mass of the elements present in the products of the chemical reaction has to be equal to the total mass of the elements present in the reactants.

(a) Chemical equation: $Zn(s)+2HCl(aq)\to ZnC{{l}_{2}}(aq)+{{H}_{2}}(g)$
Reactants side	Product side
One Zn from Zn(s)	One Zn from Zn(s)
two hydrogen atoms from HCl(aq)	two hydrogen atoms from ${{H}_{2}}(g)$
two Chlorine atom from HCl (aq)	Two Chlorine atom from $ZnC{{l}_{2}}(aq)$
(b) Chemical equation: $N{{a}_{2}}C{{O}_{3}}(s)+2HCl(aq)\to 2NaCl(aq)+{{H}_{2}}O(l)+C{{O}_{2}}(g)$
Reactants side	Product side
Two sodium atoms from $N{{a}_{2}}C{{O}_{3}}$	two Na atoms from NaCl
One C atom from $N{{a}_{2}}C{{O}_{3}}$	One C atom from $C{{O}_{2}}$
three O atoms from $N{{a}_{2}}C{{O}_{3}}$	one O atom from ${{H}_{2}}O$ and two O atoms from $C{{O}_{2}}$
Two hydrogen atoms from HCl	Two hydrogen atoms from ${{H}_{2}}O$
(c) Chemical equation: $NaHC{{O}_{3}}(s)+HCl(aq)\to NaCl(aq)+C{{O}_{2}}(g)+{{H}_{2}}O(l)$
Reactants side	Product side
one sodium atom from $NaHC{{O}_{3}}$	One Na atom from NaCl
One C atom from $NaHC{{O}_{3}}$	One C atom from $C{{O}_{2}}$
three O atoms from $NaHC{{O}_{3}}$	one O atom from ${{H}_{2}}O$ and two O atoms from $C{{O}_{2}}$
Two hydrogen atoms from HCl and $NaHC{{O}_{3}}$	Two hydrogen atoms from ${{H}_{2}}O$
(d) Chemical equation: $NaOH(aq)+HCl(aq)\to NaCl(aq)+{{H}_{2}}O(l)$
Reactants side	Product side
one sodium atom from NaOH	One Na atom from NaCl
One Cl atom from HCl	One Cl atom from NaCl
One O atom from NaOH	one O atom from ${{H}_{2}}O$
Two hydrogen atoms from HCl and NaOH	Two hydrogen atoms from ${{H}_{2}}O$
(e) Chemical equation: $CuO(s)+2HCl(aq)\to CuC{{l}_{2}}(aq)+{{H}_{2}}O(l)$
Reactants side	Product side
one Cu atom from CuO	One Cu atom from $CuC{{l}_{2}}$
Two Cl atoms from HCl	Two Cl atoms from $CuC{{l}_{2}}$
One O atom from CuO	one O atom from ${{H}_{2}}O$
Two hydrogen atoms from HCl	Two hydrogen atoms from ${{H}_{2}}O$

Hence, the complete and balanced equations are
(a) $Zn(s)+2HCl(aq)\to ZnC{{l}_{2}}(aq)+{{H}_{2}}(g)$
(b) $N{{a}_{2}}C{{O}_{3}}(s)+2HCl(aq)\to 2NaCl(aq)+{{H}_{2}}O(l)+C{{O}_{2}}(g)$
(c) $NaHC{{O}_{3}}(s)+HCl(aq)\to NaCl(aq)+C{{O}_{2}}(g)+{{H}_{2}}O(l)$
(d) $NaOH(aq)+HCl(aq)\to NaCl(aq)+{{H}_{2}}O(l)$
(e) $CuO(s)+2HCl(aq)\to CuC{{l}_{2}}(aq)+{{H}_{2}}O(l)$

Note: For example, when milk is left at room temperature or food is cooked, or food gets digestion in our body. In these situations, the nature and identity of the initial substance had changed. Whenever a chemical change takes place, that chemical reaction represents the change in a reaction.