30. A solid sample contains only CaCO3, and MgCO3. To completely react the CaCO3 and MgCO3
present in the sample. 42.00 cm of 0.088 M
HCI were required. The anhydrous chloride salts
from the reaction, obtained by evaporation of
the filtrate weighed 0.19 g. The mass of CaCO3
present in the solid sample is (C = 12,0 = 16,
Mg = 24, Ca = 40, CI = 35.5 )
(1) 0.05 g.
(2) 0.07 g
(3) 0.09 g
(4) 0.11g
(5) 0.12 g

Explanation:

Step 1

The mass percent of MgCO3 in the original mixture is calculated as shown,

Step 2

Masses of MgCO3 and CaCO3 is 24g; Moles of carbon dioxide produced from Magnesium carbonate  and Calcium carbonate are.

Step 3

Adding and equating the moles of Carbon dioxide results in,

Step 4

Percent mass of MgCO3 in the sample is calculated as,

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the objects have the same charge.