For each of the reactions, calculate the mass (in grams) of the product formed when 15.81 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant.

2K(s)+Cl2(g)––––––→2KCl(s)

so, which is underlined?

convert grams to moles
the equation tells you how many moles of product to expect
convert that to grams

To calculate the mass of the product formed when 15.81 g of the underlined reactant (Cl2) completely reacts, we need to use the balanced equation and molar mass of the reactants and products.

The balanced equation is:
2K(s) + Cl2(g) → 2KCl(s)

The molar mass of Cl2 is 70.90 g/mol.

1. Calculate the moles of Cl2:
moles of Cl2 = mass of Cl2 / molar mass of Cl2
moles of Cl2 = 15.81 g / 70.90 g/mol

2. Use the mole ratio from the balanced equation to find moles of KCl:
moles of KCl = moles of Cl2

3. Convert moles of KCl to mass of KCl:
mass of KCl = moles of KCl × molar mass of KCl
molar mass of KCl = (39.10 g/mol + 35.45 g/mol) = 74.55 g/mol

mass of KCl = moles of KCl × molar mass of KCl
mass of KCl = (15.81 g / 70.90 g/mol) × (74.55 g/mol)
mass of KCl = 33.35 g

So, when 15.81 g of Cl2 completely reacts, the mass of KCl formed is 33.35 g.