Question

Please help.

Heating 1.29 g of gallium gives a gallium-oxygen compound with a mass of 1.73 g. Calculate the empirical formula of the compound by following the next four steps. Step 1: Figure out how many grams of oxygen are in the 1.73 grams of gallium-oxygen compound. The grams of oxygen is

	A) 1.73 g + 1.29 g = 3.01 g
	B) 1.73 g / 15.99 g = 0.108
	C) 1.73 g – 1.29 g = 0.44 g

Step 2: Convert the 1.29 g of gallium to moles

	A) 1.29 g * 15.99 g/mol = 20.6 mole
	B) 1.29 g * 69.72 g/mol = 89.9 mol
	C) 1.29 g * (1 mole / 15.99 g) = 0.0807 mol
	D) 1.29 g * (1mole / 69.72 g) = 0.0185 mol

Step 3: Convert the grams of oxygen you calculated in step 1 to moles

	A) 1.29 g * (1 mole / 15.99 g) = 0.0807 mole
	B) 0.44 g * (1 mole / 15.99 g) = 0.0275 g
	C) 0.44 g * (15.99 g / 1mole) = 7.04 mole
	D) 0.44 g * (1 mole / 15.99 g) = 0.0275 mole

Figure out the formula by taking the larger mole and divided it by the smaller mole, between the mole of gallium and the mole of oxygen.

	A) 0.0275 mole of O / 0.0185 mole of Ga = 1.486 O / 1 Ga. Since it needs to be whole number ratio, both 1.486 and 1 will be multiplied by 2. It becomes 3 O/ 2 Ga. Thus the formula is Ga2O3.
	B) 0.0275 mole of Ga / 0.0185 mole of O = 1.486 Ga / 1 O. Since it needs to be whole number ratio, both 1.486 and 1 will be multiplied by 2. It becomes 3 Ga/ 2 O. Thus the formula is O2Ga3
	C) 0.0275 mole of O / 0.0185 mole of Ga = 1.486, thus the formula is GaO1.486
	D) I cannot figure it out.

Answer 1

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