This process is named taxonomy.
It is 0.5474 but you can put 0.5 hope this helps
Answer:
Because the Earth is always shifting, so research has to constantly be updated.
The mass of impure
is 20.7167 g. The decomposition reaction is as follows:

Here, 1 mole of
gives 1 mole of MgO.
Molar mass of
and MgO is 84.31 g/mol and 40.3044 g/mol respectively.
Converting number of moles in terms of mass,

Here, M is molar mass.
Since, 
Thus, 
On putting the values,

Rearranging,

Or,
...... (1)
Let the mass of impurity be
and mass of impure
is 20.7167 g thus,
...... (2)
Also, mass of impure MgO is 16.8817 g thus,
...... (3)
On comparing equations (2) and (3),

Putting the value of
in equation (1),

Or,

Or,

Or,

Or,

Thus, magnesium carbonate present in the original sample is 7.35 g.
Answer:
497 ml
Explanation:
(678 ml) x (273 / (25 + 273)) x (0.8 atm / 1 atm) = 497 ml