Answer:
15 grams.
Step-by-step explanation:
Molar mass of KClO3 = (39.10+35.45+3(16.00)) g/mol = 122.55 g/mol. Why? Because the molar mass of a compound is the sum of the molar masses of its constituents. There is 1 K atom, 1 Cl atom, and 3 O atoms in KClO3.
We can determine the mols of KClO3 given its mass and molar mass. How? Using the factor-label method (cancelling units out):
25 g * 1mol/122.55g = 0.203998368 mol.
We must now use mol ratios to determine the amount of potassium chloride (in mols) produced:
n of KCl = 0.203998368 mol(KClO3) * (2 mol KCl)/(2 mol KClO3) = 0.203998368 mol.
Molar mass of KCl = (39.10 + 35.45) g/mol = 74.55 g/mol.
From here, we can find the mass of KCl using the same logic discussed above:
m of KCl = 0.203998368 mol * 74.55 g/mol = 15.20807833 g = 15 g (rounded in accord with significant figures)