A hydrocarbon contain 86% carbon, 488 ml of the hydrocarbon weight 1.68 g at STP. Then the hydrocarbon is an

Options

A. (a)Alkane
B. (b)Alkene
C. (c )Alkyne
D. (d)Arene

Explanation

To determine the type of hydrocarbon based on the given information, we can follow these steps:

### Step 1: Determine the percentage composition of the hydrocarbon
The hydrocarbon contains 86% carbon and 14% hydrogen (since 100% - 86% = 14%).

### Step 2: Assume a sample mass
Assume we have 100 g of the hydrocarbon. This means we have:
- 86 g of carbon
- 14 g of hydrogen

### Step 3: Calculate the number of moles of carbon and hydrogen
To find the number of moles, we use the formula:
\[ \text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]
- Molar mass of carbon (C) = 12 g/mol
- Molar mass of hydrogen (H) = 1 g/mol

Calculating the moles:
- Moles of carbon:
\[ \text{Moles of C} = \frac{86 \text{ g}}{12 \text{ g/mol}} \approx 7.17 \text{ moles} \]
- Moles of hydrogen:
\[ \text{Moles of H} = \frac{14 \text{ g}}{1 \text{ g/mol}} = 14 \text{ moles} \]

### Step 4: Determine the mole ratio
To find the simplest whole number ratio of moles of carbon to moles of hydrogen:
- The ratio of moles of C to H is:
\[ \text{Ratio} = \frac{7.17}{7.17} : \frac{14}{7.17} \approx 1 : 2 \]
This indicates that for every 1 carbon atom, there are 2 hydrogen atoms.

### Step 5: Write the empirical formula
Based on the mole ratio, the empirical formula of the hydrocarbon is:
\[ \text{Empirical formula} = \text{CH}_2 \]

### Step 6: Determine the molecular formula
Next, we need to find the molecular formula. We know the volume of the hydrocarbon is 488 ml and its weight is 1.68 g at STP.

Using the ideal gas law, we can find the molar mass:
At STP, 1 mole of gas occupies 22.4 L (or 22400 ml).
The number of moles of the hydrocarbon can be calculated as:
\[ \text{Number of moles} = \frac{\text{Volume (ml)}}{22400 \text{ ml/mol}} = \frac{488}{22400} \approx 0.0218 \text{ moles} \]

Now, we can find the molar mass of the hydrocarbon:
\[ \text{Molar mass} = \frac{\text{mass (g)}}{\text{number of moles}} = \frac{1.68 \text{ g}}{0.0218 \text{ moles}} \approx 77.05 \text{ g/mol} \]

### Step 7: Compare empirical and molecular formulas
The empirical formula mass of CH2 is:
\[ \text{Empirical formula mass} = 12 + (2 \times 1) = 14 \text{ g/mol} \]
Now, we find the ratio of the molar mass to the empirical formula mass:
\[ \text{Ratio} = \frac{77.05 \text{ g/mol}}{14 \text{ g/mol}} \approx 5.5 \]
Since the ratio should be a whole number, we round it to 6. Therefore, the molecular formula is:
\[ \text{Molecular formula} = C_6H_{12} \]

### Conclusion
The hydrocarbon is an alkene, specifically hexene (C6H12).

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