Question

consider that the mass of o in the sample must be the difference between the mass of c and h and the mass of the sample. mass o = 0.400 g - (0.0181 mol h • 1.01 g h / 1 mol h) - (0.0136 mol c • 12.01 g c / 1 mol c) = 0.218 g o atoms. 0.00905 mol h₂o formed. 0.0181 mol h in sample. 0.0136 mol c in sample. calculate the amount (mol) o in the sample.

Explanation:

Step1: Calculate mass of C

Multiply moles of C by its molar - mass.
$m_{C}=0.0136\ mol\times12.01\ g/mol = 0.163336\ g$

Step2: Calculate mass of H

Multiply moles of H by its molar - mass.
$m_{H}=0.0181\ mol\times1.01\ g/mol = 0.018281\ g$

Step3: Calculate mass of O in sample

Given the formula for mass of O in sample:
$m_{O}=0.400\ g-(0.0181\ mol\times1.01\ g/mol)-(0.0136\ mol\times12.01\ g/mol)$
$m_{O}=0.400\ g - 0.018281\ g-0.163336\ g$
$m_{O}=0.218383\ g$

Step4: Calculate moles of O

Use the molar - mass of O ($M_{O}=16.00\ g/mol$) to find moles of O.
$n_{O}=\frac{m_{O}}{M_{O}}=\frac{0.218383\ g}{16.00\ g/mol}=0.013649\ mol\approx0.0136\ mol$

Answer:

$0.0136$