Question

Zn + HNOg -> Zn(NO3)2 +H2
Using the formula in the previous question, what coefficient needs to be changed?
2HNO₃
3HNO₃ , 3H₂ , and 2 Zn
4H₂ and 2Zn
None

Answer 1

In the given reaction:

**Zn + HNO₃ → Zn(NO₃)₂ + H₂**

To balance the equation, we need to consider the number of atoms on each side. The products show that each zinc (Zn) contributes to one molecule of zinc nitrate (Zn(NO₃)₂) and one molecule of hydrogen gas (H₂).

The balanced equation is:

\[ \text{Zn} + 2 \text{HNO}_3 \rightarrow \text{Zn(NO}_3)_2 + \text{H}_2\]

Here, for every zinc atom, we need 2 molecules of nitric acid (HNO₃) to produce 1 molecule of zinc nitrate (Zn(NO₃)₂) and 1 molecule of hydrogen gas (H₂).

Based on the options you've provided:

- **2HNO₃** is the correct coefficient needed for the balanced equation.
- The other options (3HNO₃, 3H₂, 2Zn, and 4H₂ and 2Zn) are not required based on the standard balancing of this reaction.

So, the coefficient that needs to be changed is **2HNO₃** (which means adding a coefficient of 2 in front of HNO₃).