Question

(a) What is a hydrocarbon? (b) Butane is the alkane with a chain of four carbon atoms. Write a structural formula for this compound, and determine its molecular and empirical formulas.

Short answer

(a) A hydrocarbon is a compound consisting only of hydrogen (H) and carbon (C) atoms, found in various structures such as linear chains, branched chains, or rings. They are divided into categories like alkanes and unsaturated hydrocarbons (alkenes and alkynes). (b) The structural formula for butane (C4H10) is \( \mathrm{CH_3CH_2CH_2CH_3} \). Its molecular formula is C4H10, and since it is already in its simplest whole number ratio, the empirical formula is also C4H10.

Step-by-step solution

Part (a): Definition of a hydrocarbon

By definition, a hydrocarbon is a compound consisting only of hydrogen (H) and carbon (C) atoms. These molecules can be found in various structures such as linear chains, branched chains, or rings. They are commonly divided into two main categories: alkanes and unsaturated hydrocarbons, which include alkenes and alkynes.

Part (b) Step 1: Structural formula for butane

In order to draw the structural formula of butane, we need to remember that alkanes have only single bonds between the carbon atoms. Butane (C4H10) has four carbon atoms in a linear chain, with hydrogen atoms filling the remaining bonds. The structural formula for butane will be as follows: \[ \mathrm{CH_3CH_2CH_2CH_3} \]

Part (b) Step 2: Molecular formula of butane

The molecular formula of a compound shows the number of each type of atom contained in a single molecule of the compound. For butane, we have already determined that there are 4 carbon atoms and 10 hydrogen atoms. So, the molecular formula for butane is: C4H10.

Part (b) Step 3: Empirical formula of butane

The empirical formula of a compound is the simplest whole number ratio of the elements in a compound. In the case of butane, the molecular formula is already in its simplest whole number ratio (C4H10), so the empirical formula is the same as the molecular formula: C4H10.