In: Chemistry
1. Suppose all magnesium reacts to produce magnesium nitride. We calculate the amount of magnesium. Now we calculate the amount of product magnesium nitride.
Percentage of magnesium = amount of magnesium×100/ amount of magnesium nitride
Amount of magnesium is measured by taking the weight of magnesium ribbon before the reaction.
Amount of magnesium nitride is measured after removing the magnesium nitride from the reaction system after the reaction ends. The mass of magnesium mitride is measured.
If all the magnesium nitride can not be determined then measured mass of magnesium nitride is less than the actual value.
So; the denominator of the percentage formula is less and the ratio of mass of magnesium / magnesium nitride increases.
For the reason; the calculated percentage of magnesium is higher than actual.
2.
If some magnesium did not react then the mass of magnesium that reacts is less than that of actial mass of magnesium ribbon.
So; numerator of the ratio ( mass of magnesium/mass of magnesium nitride) decreases and the ratio also decreases.
So; calculated percentage of Mg is less than the actual value.