Final answer:
To calculate the moles of magnesium, divide its mass by the molar mass (24.305 g/mol). For mass-mass calculations, compare the amounts from each reactant to find the limiting yield. In a reaction forming MgCl₂, multiply the moles of magnesium by 95.211 g/mol to find the formed mass.
Step-by-step explanation:
To calculate the number of moles of magnesium, you will need to know the mass of magnesium and its molar mass. The molar mass of magnesium is 24.305 g/mol. You can calculate the moles by dividing the mass of magnesium by its molar mass. For example, if you have 24.305 grams of magnesium, the calculation would be 24.305 g ÷ 24.305 g/mol, resulting in 1 mole of magnesium.
When performing mass-mass calculations to determine the mass of magnesium formed in a reaction, you should perform the calculation for each reactant and then identify which gives the lesser amount. For instance, if you have a reaction where magnesium and another reactant could both yield magnesium chloride, you would calculate the mass of magnesium chloride that could be formed from each and then determine the smaller amount, as this would be the limiting reagent's yield.
As an example calculation, if we were to calculate the mass of magnesium chloride (MgCl₂) formed from 0.08 moles of magnesium, we would use the formula weight of MgCl₂ (95.211 g/mol) and multiply it by the number of moles (0.08 moles), resulting in approximately 7.62 grams of magnesium chloride. The atomic ratio of Mg atoms to Cl atoms in MgCl₂ is 1:2, reflecting the formula.