A sample of magnesium was burnt in air to give a mixture of MgO and Mg₃N₂. The ash was dissolved in 60 meq of HCl, and the resulting solution was back-titrated with NaOH. 12 meq of NaOH were required to reach the endpoint. An excess of NaOH was then added, and the solution was distilled. The ammonia released was trapped in a 10 meq second acid solution. Back-titration of this solution required 6 meq of the base. Calculate the percentage of magnesium burnt to nitride.

To calculate the percentage of magnesium burnt to nitride, we need to analyze the reactions and titration steps involved in the process. Firstly, the burning of magnesium in air produces a mixture of MGO and MG₃N₂. Then, the ash is dissolved in HCl and back titrated with NaOH to determine the excess acid.

The excess NaOH is then used to trap the ammonia released during distillation and back titrated with acid to determine the ammonia content.

Let's calculate the percentage of magnesium burnt to nitride:

12 meq of NaOH was needed to back titrate the HCl solution.
In the second part, 6 meq of the base was required to back titrate the solution containing the trapped ammonia.
The difference in the amount of NaOH used in both titrations represents the amount of NaOH consumed by the ammonia, which is equal to the amount of MG₃N₂ formed during the initial burning of magnesium.
The amount of MG₃N₂ in meq can be calculated by taking the difference between the amount of NaOH in the second titration (6 meq) and the amount used in the first titration (12 meq).

To calculate the percentage of magnesium burnt to nitride, divide the amount of MG₃N₂ (in meq) by the total amount of magnesium initially present, which can be calculated using the molar mass of magnesium.

Let's work out the calculations:

Assuming the molar mass of magnesium (Mg) is 24 g/mol:

Total moles of Mg initially present = 60 meq / 24 meq/mol = 2.5 mol
Amount of MG₃N₂ formed = 12 meq - 6 meq = 6 meq
Percentage of magnesium burnt to nitride = (6 meq / 2.5 mol) x 100
Percentage of magnesium burnt to nitride = 240%

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