What is the mass of magnesium oxide (MgO) formed when 10 g of Mg is burnt?

Explanation

To find the mass of magnesium oxide (MgO) formed when 10 g of magnesium (Mg) is burnt, we can follow these steps:

### Step 1: Write the Balanced Chemical Equation
The balanced chemical equation for the reaction of magnesium with oxygen is:
\[ 2 \text{Mg (s)} + \text{O}_2 \text{(g)} \rightarrow 2 \text{MgO (s)} \]

### Step 2: Convert the Balanced Equation to Moles
From the balanced equation, we can see that:
- 2 moles of Mg produce 2 moles of MgO.
This means:
- 1 mole of Mg produces 1 mole of MgO.

### Step 3: Calculate the Molar Masses
Next, we need to find the molar masses:
- Molar mass of Mg = 24 g/mol
- Molar mass of MgO = 24 g (for Mg) + 16 g (for O) = 40 g/mol

### Step 4: Find the Mass of MgO Produced from 10 g of Mg
Now, we can use the mass-to-mass relationship. From the balanced equation:
- 48 g of Mg (2 moles) produces 80 g of MgO (2 moles).

Using this relationship, we can set up a proportion:
\[ \frac{48 \text{ g Mg}}{80 \text{ g MgO}} = \frac{10 \text{ g Mg}}{x \text{ g MgO}} \]

### Step 5: Solve for x (Mass of MgO)
Cross-multiplying gives us:
\[ 48 \cdot x = 80 \cdot 10 \]
\[ 48x = 800 \]
\[ x = \frac{800}{48} = 16.67 \text{ g} \]

### Conclusion
The mass of magnesium oxide (MgO) formed when 10 g of magnesium is burnt is approximately **16.67 grams**.

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