Answer:
0.73
Step-by-step explanation:
the formula to work out moles:
moles = mass/relative formula mass
mass = 125g
the relative atomic mass for Ba is 137
the relative atomic mass for O is 16
the relative atomic mass for H is 1
oxygen and hydrogen have two atoms each : Ba(OH)2
the relative formula mass is the sum of the atomic masses in the compound:
137 + (16 × 2) + (1 × 2) = 171
moles = 125g/171 = 0.73 to two decimal places