A 70.170.1 gram sample of H2O𝐻2𝑂 contains how many molecules of water? 1.16×10−22molecules1.16×10−22molecules 4.22×1025molecules4.22×1025molecules 7.61×1026molecules7.61×1026molecules 2.34×1024molecules2.34×1024molecules 2.1×10−21molecules
Question
A 70.170.1 gram sample of H2O𝐻2𝑂 contains how many molecules of water? 1.16×10−22molecules1.16×10−22molecules 4.22×1025molecules4.22×1025molecules 7.61×1026molecules7.61×1026molecules 2.34×1024molecules2.34×1024molecules 2.1×10−21molecules
Solution
To find the number of molecules in a given mass of a substance, we can use the formula:
Number of molecules = (mass of sample / molar mass of substance) * Avogadro's number
The molar mass of water (H2O) is approximately 18.015 grams/mole. Avogadro's number is 6.022 x 10^23 molecules/mole.
Step 1: Convert the mass of the sample to moles: 70.1 grams H2O * (1 mole H2O / 18.015 grams H2O) = 3.89 moles H2O
Step 2: Convert moles to molecules using Avogadro's number: 3.89 moles H2O * (6.022 x 10^23 molecules H2O / 1 mole H2O) = 2.34 x 10^24 molecules H2O
So, a 70.1 gram sample of H2O contains approximately 2.34 x 10^24 molecules of water.
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