Question

1) What is the mass in grams of 5.5×10²⁰ molecules of aspirin (C9H8O4

2) What is the mass of 5.90 moles of magnesium chloride, MgCl2?

3) How many moles of nitrogen, N, are in 85.0 g of nitrous oxide, N2O?

4) Cyclopropane, C3H6, is an anesthetic given by inhalation. How many grams are in 0.20 moles of cyclopropane?

5) The sedative Demerol hydrochloride has the formula C15H22ClNO2. How many grams are in 0.024 moles of Demerol hydrochloride?

Answer 1

molar mass of aspirin C9H8O4 = 9*12.01 + 8*1.01 + 4.16 = 180.16 g/mol

so mass of 1 mole aspirin = 180.16 g
1 mole = 6.022 x10^23 number of molecules
so mass of 5.5×1020 molecules of aspirin = 180.16 g/6.022 x10^23 *5.5×10^20

=164.54 x10^-3 g
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2)
MgCl2 molar mass= 1*24.30 + 2*35.45 = 95.21 g/mol

so 1mol has mass= 95.21 g
then 5.90 mol MgCl2 has mass = 5.9 mols *95.21 g/mol = 561.739 g

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N2O , molar mass= 2*41.01 + 1*16 = 44.01 g/mol

so 1 mole N2O has mass= 44.01 g

Hence 85 g N2O = 1mole/44.01 g*85 g = 1.93 mols
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C3H6 molar mass=42.08 g/mol

1 mole C3H6 = 42.08 g/mol
then 0.2 mol C3H6 has mass = 0.2 mol * 42.08 g/mol = 8.416 g
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molar mass of C15H22ClNO2= 15*12.01+ 22*1.01 + 1*35.05 + 1*14.01 + 2*16
=283.79 g/mol

thus 1 mol C15H22ClNO2 has mass = 283.79 g/mol

mass of 0.024 mol C15H22ClNO2 = 0.024mols *283.79 g/mol
= 6.81 g
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