To determine the masses of the products (Mg and Cl2) produced from 20 grams of MgCl2, we can use the law of conservation of mass. This law states that in a closed system, mass is neither created nor destroyed during a chemical reaction.
The balanced reaction is:
\[ \text{MgCl}_2 \rightarrow \text{Mg} + \text{Cl}_2 \]
First, we need to calculate the molar mass of MgCl2:
- Molar mass of Mg = 24.31 g/mol
- Molar mass of Cl = 35.45 g/mol
- Therefore, the molar mass of MgCl2 = 24.31 g/mol + (2 × 35.45 g/mol) = 24.31 g/mol + 70.90 g/mol = 95.21 g/mol
Now we can find out how many moles of MgCl2 are present in 20 grams:
\[ \text{Moles of MgCl}_2 = \frac{20 \text{ g}}{95.21 \text{ g/mol}} \approx 0.210 moles \]
According to the balanced reaction, 1 mole of MgCl2 produces 1 mole of Mg and 1 mole of Cl2. Therefore, 0.210 moles of MgCl2 will produce:
- 0.210 moles of Mg
- 0.210 moles of Cl2
Next, we calculate the mass of the products:
-
Mass of Mg: \[ \text{Mass of Mg} = 0.210 \text{ moles} \times 24.31 \text{ g/mol} \approx 5.10 \text{ g} \]
-
Mass of Cl2: \[ \text{Mass of Cl}_2 = 0.210 \text{ moles} \times (2 \times 35.45 \text{ g/mol}) \approx 14.90 \text{ g} \]
Now we can check the total mass of the products:
\[ \text{Total mass of products} = \text{Mass of Mg} + \text{Mass of Cl}_2 \approx 5.10 \text{ g} + 14.90 \text{ g} = 20 \text{ g} \]
Based on this analysis, the statement that is true is:
The sum of the masses of Mg and Cl2 will be 20 grams.