AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
No, the equation Mg + O₂ → MgO is not balanced.
Reason: On the LHS there are 2 atoms of oxygen (in O₂), but on the RHS there is only 1 atom of oxygen (in MgO). Since the number of atoms of each element is not equal on both sides, it violates the law of conservation of mass.
Balancing the equation:
| Element | LHS | RHS |
|---------|-----|-----|
| Mg | 1 | 1 |
| O | 2 | 1 |
To balance oxygen, place coefficient 2 before MgO, then balance Mg:
$$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$$
This is the correctly balanced equation (Mg: 2 = 2; O: 2 = 2). ✓
Source: Chapter 1, Sections 1.1.1 and 1.1.2
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Key examiner tip: Always state which element is unbalanced and why it violates the law of conservation of mass. Never change the formula of a compound (e.g., do not write MgO₂); only add coefficients.