A mineral in a fine state of division (0.6324 g) was dissolved in 25.0 mL of 4.0 mol / L boiling HCl and diluted with 175.0 mL of H2O containing two drops of methyl red indicator. The solution was heated to 100 ° C and a heated solution containing 2.00 g of (NH4) 2C2O4 was added slowly to precipitate CaC2O4. Next, NH3 6.0 mol / L was added until the indicator changed from red to yellow, indicating that the liquid was neutral or slightly basic. After slow cooling for 1 hour, the liquid was decanted, the solid transferred to a crucible and washed five times with 0.10 wt% (NH4) 2C2O4 solution, until no Cl- was detected in the filtrate with the addition of AgNO3 solution. The crucible was dried at 105 ° C for 1 hour and then taken to an oven at 500 ° C ± 25 ° C for two hours. The mass of the empty crucible was 18.2311 g. The crucible mass with CaCO3 (s) was weighed 5 times to an average of 18.5467 g. Determine the percentage, by mass, of Ca in the mineral. Ca (40.078 g / mol); C (12.01078 g / mol); O (15.99943 g / mol); H (1.007947 g / mol), N (14,000672 g / mol)
A mineral in a fine state of division (0.6324 g) was dissolved in 25.0 mL of 4.0 mol / L boiling HCl and diluted with 175.0 mL of H2O containing two drops of methyl red indicator. The solution was heated to 100 ° C and a heated solution containing 2.00 g of (NH4) 2C2O4 was added slowly to precipitate CaC2O4. Next, NH3 6.0 mol / L was added until the indicator changed from red to yellow, indicating that the liquid was neutral or slightly basic. After slow cooling for 1 hour, the liquid was decanted, the solid transferred to a crucible and washed five times with 0.10 wt% (NH4) 2C2O4 solution, until no Cl- was detected in the filtrate with the addition of AgNO3 solution. The crucible was dried at 105 ° C for 1 hour and then taken to an oven at 500 ° C ± 25 ° C for two hours.
The mass of the empty crucible was 18.2311 g. The crucible mass with CaCO3 (s) was weighed 5 times to an average of 18.5467 g. Determine the percentage, by mass, of Ca in the mineral.
Ca (40.078 g / mol); C (12.01078 g / mol); O (15.99943 g / mol); H (1.007947 g / mol), N (14,000672 g / mol)
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