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3.39 Cinnamic alcohol is used mainly in perfumery, particularly in soaps and cosmetics. Its molecular formula is CH100. (a) Calculate the percent composition by mass of c, h, and o in cinnamic alcohol. (b) How many molecules of cinnamic alcohol are contained in a sample of mass 0.469 g? hydrogen is 1.008 solve it accurately
Accepted Answer
Here's the breakdown of how to solve the problem:
(a) Percent Composition by Mass
1. Calculate the molar mass of cinnamic alcohol:
- C: 12.01 g/mol
9 = 108.09 g/mol
- H: 1.008 g/mol
10 = 10.08 g/mol
- O: 16.00 g/mol
1 = 16.00 g/mol
- Molar mass of cinnamic alcohol = 108.09 + 10.08 + 16.00 = 134.17 g/mol
2. Calculate the percent composition of each element:
- %C = (108.09 g/mol / 134.17 g/mol)
100% = 80.52%
- %H = (10.08 g/mol / 134.17 g/mol)
100% = 7.52%
- %O = (16.00 g/mol / 134.17 g/mol)
100% = 11.96%
(b) Number of Molecules
1. Convert the mass of the sample to moles:
- Moles = mass / molar mass = 0.469 g / 134.17 g/mol = 0.00350 mol
2. Use Avogadro's number to convert moles to molecules:
- Number of molecules = moles
Avogadro's number
- Number of molecules = 0.00350 mol
6.022 x 10^23 molecules/mol = 2.11 x 10^21 molecules
Therefore:
The percent composition by mass of cinnamic alcohol is: C (80.52%), H (7.52%), and O (11.96%).
A sample of 0.469 g contains 2.11 x 10^21 molecules of cinnamic alcohol.
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