Answer
Sr.
Work Step by Step
Number of moles of $CO_2$:
$n=PV/RT$
$n=(69.8/760×1\ atm)×0.285\ L\div((0.082)(298\ K))$
$n=0.00107\ mol$
This is also the number of moles of the carbonate.
The molar mass of the compound is:
$0.158\ g/0.00107\ mol=147.60\ g/mol$
Since $CO_3^{2-}$ has a molecular weight of $60.01\ g/mol$, it follows:
Atomic weight of M:
$147.60-60.01=87.59\ g/mol$
Which is closest to Strontium's atomic weight.
