Complete the following reactions,
(i) `H_2(g)+MnO(s)overset(Delta)rarrMn(s)+H_2O(g)`
(ii) `CO(g)+H_2(g)underset("Catalyst")overset(Delta)rarr`
(iii) `C_3H_8(g)+3H_2O(g)underset("Catalyst")overset(Delta)rarr`
(iv) `Zn(s)+NaOH(aq)overset("Heat")rarr`
After completing the above reactions in the balanced equations the coefficient for `H_2(g)` may be

Options

A. 1,2,7,1
B. 1,2,4,2
C. 1,2,1,1
D. 1,3,4,2

Answer

To solve the given reactions and find the stoichiometric coefficient of \( H_2(g) \), we will complete each reaction step by step.

### Reaction (i)
**Given Reaction:**
\[ H_2(g) + MnO(s) \overset{\Delta}{\rightarrow} Mn(s) + H_2O(g) \]

**Step 1:** Identify the reactants and products.
- Reactants: Hydrogen gas \( H_2 \) and manganese oxide \( MnO \).
- Products: Manganese \( Mn \) and water vapor \( H_2O \).

**Step 2:** Balance the reaction.
- The reaction is already balanced as there is 1 molecule of \( H_2 \) producing 1 molecule of \( H_2O \).

**Balanced Reaction:**
\[ H_2(g) + MnO(s) \rightarrow Mn(s) + H_2O(g) \]

### Reaction (ii)
**Given Reaction:**
\[ CO(g) + H_2(g) \underset{\text{Catalyst}}{\overset{\Delta}{\rightarrow}} \]

**Step 1:** Identify the products.
- This is a synthesis reaction where carbon monoxide reacts with hydrogen gas to form methanol \( CH_3OH \).

**Step 2:** Write the balanced equation.
- The balanced equation is:
\[ CO(g) + 2H_2(g) \rightarrow CH_3OH(l) \]

### Reaction (iii)
**Given Reaction:**
\[ C_3H_8(g) + 3H_2O(g) \underset{\text{Catalyst}}{\overset{\Delta}{\rightarrow}} \]

**Step 1:** Identify the products.
- This reaction is a steam reforming reaction, which typically produces carbon monoxide and hydrogen gas.

**Step 2:** Write the balanced equation.
- The balanced equation is:
\[ C_3H_8(g) + 3H_2O(g) \rightarrow 3CO(g) + 7H_2(g) \]

### Reaction (iv)
**Given Reaction:**
\[ Zn(s) + NaOH(aq) \overset{\text{Heat}}{\rightarrow} \]

**Step 1:** Identify the products.
- Zinc reacts with sodium hydroxide to form sodium zincate and hydrogen gas.

**Step 2:** Write the balanced equation.
- The balanced equation is:
\[ Zn(s) + 2NaOH(aq) \rightarrow Na_2ZnO_2(aq) + H_2(g) \]

### Summary of Coefficients
Now, let's summarize the coefficients of \( H_2(g) \) from each reaction:
1. Reaction (i): Coefficient of \( H_2(g) \) = 1
2. Reaction (ii): Coefficient of \( H_2(g) \) = 2
3. Reaction (iii): Coefficient of \( H_2(g) \) = 7
4. Reaction (iv): Coefficient of \( H_2(g) \) = 1

### Final Answer
The coefficients of \( H_2(g) \) from the completed reactions are 1, 2, 7, and 1 respectively.