Many metal carbonates, such as magnesium carbonate, decompose to form the metal oxide when heated. $$\[ \mathrm{MgCO}_{3}(\mathrm{~s}) \rightarrow \mathrm{MgO}(\mathrm{~s})+\mathrm{CO}_{2}(\mathrm{~g}) \]$$ Other metal carbonates, such as sodium carbonate, $$\(\mathrm{Na}_{2} \mathrm{CO}_{3}\)$$, do not decompose at the temperature produced by a Bunsen burner. FB 3 is a mixture that contains only sodium carbonate, $$\(\mathrm{Na}_{2} \mathrm{CO}_{3}\)$$, and magnesium carbonate. You will carry out an experiment involving thermal decomposition to find the percentage of each of these metal carbonates in this mixture. Method - Weigh the empty crucible with its lid. Record the mass. - Transfer all the FB 3 from the container into the crucible. - Weigh the crucible, lid and FB 3. Record the mass. - Calculate and record the mass of FB 3 used. - Place the crucible and contents on the pipe-clay triangle. - Heat the crucible gently, with the lid on, for approximately 1 minute. - Heat strongly, with the lid off, for a further 5 minutes. - Leave the crucible with its contents until it is cool. While the crucible is cooling, you may wish to begin work on Question 3. - When the crucible is cool, weigh the crucible with its lid and contents. Record the mass. - Heat the crucible strongly, with the lid off, for approximately 4 minutes. - Allow the crucible and contents to cool. - When the crucible is cool, weigh the crucible with its lid and contents. Record the mass. - Calculate and record the mass of residue. - Calculate and record the mass of carbon dioxide produced. Leave the crucible and contents to become completely cool for use in Question 2(c). Results

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