Calculate the mass of Mg (atomic mass = 24 g'mol) that combines with 1.5 mol of `O_2` to form magnesium oxide (MgO)

Options

A. 24 g
B. 36 g
C. 48 g
D. 72 g

Answer

To solve the problem of calculating the mass of magnesium (Mg) that combines with 1.5 moles of dioxygen (O₂) to form magnesium oxide (MgO), we can follow these steps:

### Step-by-Step Solution:

1. **Write the Balanced Chemical Equation**:
The reaction between magnesium and oxygen can be represented by the balanced equation:
\[ 2 \text{Mg} + \text{O}_2 \rightarrow 2 \text{MgO} \]
This indicates that 2 moles of magnesium react with 1 mole of oxygen.

2. **Determine the Moles of Magnesium Needed**:
From the balanced equation, we see that 1 mole of O₂ requires 2 moles of Mg. Therefore, for 1.5 moles of O₂, the required moles of Mg can be calculated using a unitary method:
\[ \text{Moles of Mg} = 1.5 \, \text{moles O}_2 \times \frac{2 \, \text{moles Mg}}{1 \, \text{mole O}_2} = 3 \, \text{moles Mg} \]

3. **Calculate the Mass of Magnesium**:
We know that the mass of a substance can be calculated using the formula:
\[ \text{Mass} = \text{Moles} \times \text{Molar Mass} \]
The atomic mass of magnesium (Mg) is given as 24 g/mol. Thus, the mass of 3 moles of magnesium is:
\[ \text{Mass of Mg} = 3 \, \text{moles} \times 24 \, \text{g/mol} = 72 \, \text{g} \]

4. **Conclusion**:
Therefore, the mass of magnesium that combines with 1.5 moles of O₂ to form magnesium oxide (MgO) is **72 grams**.

### Final Answer:
The mass of magnesium required is **72 grams**.

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