Identify Group 2 Metal from Thermal Decomposition of Nitrate

https://www.youtube.com/watch?v=KfnDKChUCQ8

Let's take a look at this week's question.

identify gp 2 metal from nitrate decomposition question

We want to identify the Group 2 metal using information from the thermal decomposition of its nitrate.

identify gp 2 metal from nitrate decomposition equation

Since the nitrate lost 3.29g of its mass as gases NO2 and O2, the remaining mass of 1.71g will be due to the residual metal oxide, MO.

We can make use of the following formula which states that the mass ratio of a component in a compound is equal to the molar mass ratio of that component in the compound.

identify gp 2 metal from nitrate decomposition mass ratio formula

This means that the mass ratio of our group 2 metal oxide to its nitrate is equal to the molar mass ratio of group 2 metal oxide to its nitrate.

We can calculate the mass ratio of metal oxide to metal nitrate from experimental data.

identify gp 2 metal from nitrate decomposition calculate mass ratio

Next we can determine the molar mass ratio of the respective Group 2 metal oxides to their nitrates.

identify gp 2 metal from nitrate decomposition calculate molar mass ratio

Finally we compare the molar mass ratios calculated and see which one is the same as our mass ratio of 0.342.

identify gp 2 metal from nitrate decomposition identify metal

Therefore the unknown Group 2 metal is calcium (option B).

Topic: Group 2 Metals, Inorganic Chemistry, A Level Chemistry, Singapore

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