Determination of the Formula of a Chemical Compound Pre-lab Assignment The molar

Question

Determination of the Formula of a Chemical Compound Pre-lab Assignment The molar mass of a pure substance, the mass of one mole of that element or compound is found by adding together the atomic masses for each atom in Its chemical formula. The empirical formula of a compound can be found by determining the simplest whole number mole ratio of the atoms in the compound. Find the atomic mass of each of the atoms in the Periodic Table. Copper Oxygen For 0.6349 g of a compound containing only copper and oxygen, CU_2O_2. A student found that contained 0.5639 g Cu How many moles of Cu are there in the sample? How many grams of O are there in the sample? How many moles of O are there in the sample? What is the Cu O mole ratio (moles Cu / motes O) in the sample? What is the empirical formula for the copper oxide? Assuming that the empirical formula is also the molecular formula for the copper oxide. what is the molar mass of the copper oxide?

Explanation / Answer

1) Cu = 63.5 g/mole

O = 16 g/mole

2) mass of Cu = 0.5639

Thus, moles of Cu = mass/molar mass = 0.5639/63.5 = 8.88*10-3

mass of O = total mass - mass of Cu = 0.6349-0.5639 = 0.071 g

moles of O = mass/molar mass = 0.071/16 = 4.44*10-3

Thus, moles of Cu:moles of O = 0.009/0.004 =2:1

Thus, empirical formula = Cu2O

Molar mass = 143 g/mole

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