Question

M is an alkaline earth metal. In step one, 2.73 kg of M reacts with oxygen gas. In step two, the product of the step 1 is dissolved in water. In step three, the product of the step two reacts with phosphoric acid and 4 kg of phosphate salt is produced. If the yield of all steps is 100%, identify M. (In solving this problem, please write down all three reactions and balance them).

Answer 1

M --> M+2

m = 2.73 kg of M

M + 1/2O2 = MO

step 2:

MO + H2O = M(OH)2(aq)

Step 3.

3M(OH)2(aq) + 2H3PO4(aq) --> 3H2O + M3(PO4)2

m = 4 kg of M3(PO4)2

if 100% yield then...

relate

2.73 kg of M

4 kg of M3(PO4)2

note htat

mass of PO4-3 = (4-2.73) = 1.27 kg

mol of PO4-3 = mass/MW = 1270/94.9714 = 13.37 mol of PO4-3

then..

2 mol of PO4-3 = 3 mol of M

mol of M = 3/2*13.37 = 20.055mol of M

MW of M = mass/mol = 2730/20.055= 136.13 g/mol

Nearest value is Barium

this must be Barium metal