3. A student performs an experiment similar to what you will be doing in lab, ex

Question

3. A student performs an experiment similar to what you will be doing in lab, except using calcium metal instead of magnesium metal. The student weights out 0.108 g of calcium. How many moles of calcium is this? ( I got answer for this one is 1.62621*10^21 Ca but not sure right or wrong )

4. In the experiment in question 3, the student collects 0.130 grams of a product containing calcium and oxygen. How many grams of oxygen were added to the calcium? ( I got answer for this problem is 0.0137 (g) of oxygen added to the calcium so is it right ?)

5. How many moles of oxygen (O) are added to calcium in question 4?

6. What is the empirical formula for the product formed from calcium and oxygen based only upon the experiment done in questions 3 - 5?

Explanation / Answer

3)

we know that

moles = mass / molar mass

also

molar mass of calcium = 40 g/mol

so

moles of calcium = 0.108 / 40 = 2.7 x 10-3

so

there are 2.7 x 10-3 moles of calcium

4)

mass of oxygen added = mass of product - mass of calcium

mass of oxygen added = 0.13 - 0.108

mass of oxygen added = 0.022 g

5)

molar mass of oxygen is 16 g/mol

so

moles of oxygen = 0.022 / 16

moles of oxygen = 1.375 x 10-3

6)

now

consider the ratio of moles

Ca:O = 2.7 x 10-3 : 1.375 x 10-3

Ca:O = 2 : 1

so

the empirical formula of the product formed is Ca20

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