Answer:
g HCN = MW HCN g/mole HCN * [8.00E19 molecules/6.022E23 molecules/mole HCN] = ??
EmForm = CaxPy
moles Ca = 0.66g / atwt Ca g/mole = ??
moles P = (1.00-0.66)g / atwt P g/mole = ??
x/y = moles Ca / moles P = ?? (express as ratio of two numbers; if both are not intergers multiply each by the same number that make them integers. This ratio gives the empirical formula.
Ca3P2
Plug and SOLVE
