Determine an Empirical Formula Flashcards

All 5 cards in this deck

What are the steps to calculate an empirical formula from reacting masses?

e.g. 0.92 g Na combines with 0.32 g O ($A_r$: Na = 23, O = 16)

1. Divide each mass by its $A_r$: $0.92/23 = 0.04$; $0.32/16 = 0.02$
2. Divide both by the smaller: $2 : 1$
3. Write as a formula: $\mathrm{Na_2O}$

In an empirical formula calculation, what do you do if the ratio comes out as 1 : 1.5?

Multiply both numbers by 2 to give whole numbers, 2 : 3.

In the magnesium oxide experiment, how is the mass of oxygen that combined worked out?

Mass of magnesium oxide formed minus mass of magnesium used.

Why must magnesium be heated to constant mass in the empirical formula experiment?

To make sure all the magnesium has reacted; otherwise the mass of oxide is too low.

Give one source of error in the magnesium oxide empirical formula experiment that makes the measured mass of oxide too low.

White smoke of magnesium oxide escapes when the lid is lifted.