Question

In a chemical reaction, exactly 2 mol of substance A react to produce exactly 3 mol of substance B. How many molecules of substance B are produced when 25.5 g of substance A reacts? The molar mass of substance A is 24.5 g/mol.

Answer 1

n(A) = 25.5 g / 24.5 g/mol = 1.0408 mol;
If 2A = 3B,
hence:
n(B) = 1.0408 *3 / 2 = 1.56 mol;
N = n *N_A
N = 1.56 mol * 6.02 *10^23 mol^-1 = 9.39 * 10^23 molecules.