Question

In a hurry to complete the experiment , slyvia did not allow all of the magnesium to react. Will her reported magnesium to oxygen ratio be too high or too low ? explain

Answer 1

She does not get high or low ration than the expected.

While combining Mg with oxygen it does so in a definite proportion, so what ever the Mg reacted sofar is in definite ration it does not vary after complete reaction of Mg with Oxygen.

For example:

We have 10 g. of Mg and let us assume only 5 g. of Mg are reacted so far,

2 Mg + O2 ---------> 2 MgO

Accirding to above eqaution,

2*24 g. of Mg needs 32 g. of O2

then, 5 g. of Mg needs 32 * 5 / 48 = 3.33 g. of O2

Mass ratio of Mg to O2 = 5 : 3.33 = 1.50 : 1.00 = 3.00 : 2.00

If we assume that all of the Mg reacts with Oxygen.

then, 10 g.of Mg needs 10 * 32 / 48 = 6.67 g. of O2

Now, the mass ratio of Mg to O2 = 10.0 : 6.67 = 1.50 : 1 = 3.00 : 2.00

SO we got the same.

Because while combining an element with other element it combines in definite proportions.

It is according to Law of definite proportions proposed by Proust.