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Question: Calculate the weight of following samples: A) 100 atoms of carbon B) 0.5 mole atoms of sulphur C) 8 ...

Calculate the weight of following samples: A) 100 atoms of carbon B) 0.5 mole atoms of sulphur C) 8 gram atom of oxygen D) 25 amu of chlorine

A

100 atoms of carbon

B

0.5 mole atoms of sulphur

C

8 gram atom of oxygen

D

25 amu of chlorine

Answer

A) 1200 amu (or 1.993 × 10^{-21} g), B) 16 g, C) 128 g, D) 25 amu (or 4.151 × 10^{-23} g)

Explanation

Solution

Here are the calculations for the weight of each sample:

A) Weight of 100 atoms of carbon The atomic mass of carbon (C) is approximately 12 amu. The weight of one carbon atom is 12 amu. The weight of 100 carbon atoms is: Weight = 100×12 amu=1200 amu100 \times 12 \text{ amu} = 1200 \text{ amu} To convert this to grams, we use the relationship 1 amu=1.6605×10−24 g1 \text{ amu} = 1.6605 \times 10^{-24} \text{ g}. Weight = 1200×1.6605×10−24 g≈1.993×10−21 g1200 \times 1.6605 \times 10^{-24} \text{ g} \approx 1.993 \times 10^{-21} \text{ g}

B) Weight of 0.5 mole atoms of sulphur The molar mass of sulphur (S) is approximately 32 g/mol. The weight of 0.5 mole of sulphur atoms is: Weight = 0.5 mol×32 g/mol=16 g0.5 \text{ mol} \times 32 \text{ g/mol} = 16 \text{ g}

C) Weight of 8 gram atom of oxygen The term "gram atom" is an older term for "mole of atoms". So, 8 gram atom of oxygen means 8 moles of oxygen atoms. The molar mass of oxygen atoms (O) is approximately 16 g/mol. The weight of 8 moles of oxygen atoms is: Weight = 8 mol×16 g/mol=128 g8 \text{ mol} \times 16 \text{ g/mol} = 128 \text{ g}

D) Weight of 25 amu of chlorine The weight of this sample is given as 25 amu. Weight = 25 amu To convert this to grams, we use the relationship 1 amu=1.6605×10−24 g1 \text{ amu} = 1.6605 \times 10^{-24} \text{ g}. Weight = 25×1.6605×10−24 g≈4.151×10−23 g25 \times 1.6605 \times 10^{-24} \text{ g} \approx 4.151 \times 10^{-23} \text{ g}