Question

A piece of rock has a mass of 2.00g. It contains calcium carbonate, but no other

Answer 1

The percentage of Calcium carbonate in the 2.00 g piece of rock : 45%

Further explanation

Reaction

CaCO₃ + 2HCl ⇒ CaCl₂ +CO₂ + H₂O

V HCL = 36 cm³

M HCl = 0.5 mol/dm³

mol of HCl :

$\tt 0.036~dm^3(36~cm^3)\times 0.5~mol/dm^3=0.018$

mol ratio CaCO₃ : HCl = 1 : 2, so mol CaCO₃ :

$\tt \dfrac{1}{2}\times 0.018=0.009$

mass CaCO₃ (MW=100 g/mol) :

$\tt 0.009\times 100=0.9~g$

The percentage of Calcium carbonate :

$\tt \%mass=\dfrac{mass~CaCO_3}{mass~rock}\times 100\%\\\\\%mass=\dfrac{0.9}{2}\times 100\%=45\%$