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An organic compound is known to contain only carbon, hydrogen and oxygen - VCE - SSCE Chemistry - Question 11 - 2005 - Paper 1
Question 11
An organic compound is known to contain only carbon, hydrogen and oxygen. The compound contains, by mass, 39.1% of carbon and 8.7% of hydrogen. The number of carbon ... show full transcript
Worked Solution & Example Answer:An organic compound is known to contain only carbon, hydrogen and oxygen - VCE - SSCE Chemistry - Question 11 - 2005 - Paper 1
Step 1
Calculate Moles of Carbon
Answer
To find the moles of carbon, we use the formula:
ext{Moles of Carbon} = rac{ ext{mass percentage of Carbon}}{ ext{molar mass of Carbon}}Given:
- Mass percentage of Carbon = 39.1%
- Molar mass of Carbon = 12.01 g/mol
Calculating the moles:
ext{Moles of Carbon} = rac{39.1}{12.01} \approx 3.25 ext{ moles}Step 2
Calculate Moles of Hydrogen
Answer
Next, we calculate the moles of hydrogen using a similar method:
ext{Moles of Hydrogen} = rac{ ext{mass percentage of Hydrogen}}{ ext{molar mass of Hydrogen}}Given:
- Mass percentage of Hydrogen = 8.7%
- Molar mass of Hydrogen = 1.008 g/mol
Calculating the moles:
ext{Moles of Hydrogen} = rac{8.7}{1.008} \approx 8.63 ext{ moles}Step 3
Step 4
Determine the Simplest Ratio
Answer
We now have the moles of each element:
- Moles of Carbon = 3.25 moles
- Moles of Hydrogen = 8.63 moles
- Moles of Oxygen = 3.26 moles
To find the simplest whole number ratio, we divide each by the smallest value (3.25):
ext{Ratio of Carbon} = \frac{3.25}{3.25} = 1\ ext{Ratio of Hydrogen} = \frac{8.63}{3.25} \approx 2.65 \ ext{Ratio of Oxygen} = \frac{3.26}{3.25} \approx 1\To approximate to whole numbers, we can round Hydrogen to 3. Thus, the empirical formula is C1H3O1.
Step 5