A Paper

Lab #16: Gravimetric Analysis of Metal Carbonate
Introduction:
In this laboratory the identity of group 1 metal Carbonate is determined gravimetrically using a double replacement precipitation reaction.
Concepts:
Double-Replacement reaction
Gravimetric analysis.
Background:
The identity of group 1 metal M is determined by analyzing an unknown Group 1 metal carbonate, M2CO3.
There are 3 main reactions in this lab:
1. Equation 1: M­2CO3 (s) → 2M+ (aq) + CO32- (aq)

2. Equation 2: Ca2+ (aq) + CO32-(aq) → CaCO3 (s)

3. Equation 3: CaCl2 (aq) + M2CO3→ CaCO3 (s) + 2MCl (aq)

The precipitated calcium carbonate is then filtered, dried, and weighed. The moles of calcium carbonate, CaCO3, are equal to the moles of Group 1 metal carbonate, M2CO3, added to the original solution. Dividing the mass of the unknown carbonate by the moles of calcium carbonate yields the formula weight, and thus the identity, of the Group 1 metal carbonate.
Experiment Overview
The purpose of this lab is to determine the identity of a Group 1 metal carbonate compound by gravimetric analysis. The unknown is weighed and dissolved in water. A solution of calcium chloride is added to the metal carbonate solution to precipitate the carbonate ions as calcium carbonate. The precipitate is filtered, dried, and weighed. From the data, the formula weight and identity of the unknown metal carbonate is determined.

Pre-lab question

Mass of crucible + M2CO3
12.627 g
Mass of crucible
10.655 g
Mass of M2CO3
1.972 g
Mass of filter paper + CaCO3
2.436 g
Mass of the filter paper
0.598 g
Mass of the CaCO3
1.838 g
Moles of CaCO3
Mol
Molar mass of M2CO3 g/mol Identity of M2CO3

Percent error
%

1. From the mass of CaCO3, calculate the moles of CaCO3 precipitated.
2. Calculate the molar mass of the unknown
3. Calculate the molar mass of the following Group 1 metal carbonates:
a. Li2CO3
b. Na2CO3
c. K2CO3
4. What is the identity of M2CO3?
5. Calculate the