A Level Chemistry OCR Practice Exam

Which of the following describes a carbocation?

1. An organic ion with a negative charge

2. An organic ion in which a carbon atom has a positive charge

3. A type of hydrocarbon

4. A molecular compound

The correct answer is: An organic ion in which a carbon atom has a positive charge

A carbocation is defined as an organic ion in which a carbon atom has a positive charge. This occurs when a carbon atom has only three bonds and is missing a fourth electron, resulting in an overall positive charge. Carbocations are often formed during chemical reactions, such as when a leaving group departs in a substitution or elimination process. Their stability can vary widely, depending on factors like the presence of alkyl groups, which can provide hyperconjugation or inductive effects that stabilize the positive charge. The first option refers to a negatively charged ion, which is not characteristic of a carbocation. The third option suggests that a carbocation is a type of hydrocarbon, which is misleading since a carbocation is a charged species rather than a neutral molecule typically associated with hydrocarbons. The last choice describes a molecular compound, which differs from the ionic nature of carbocations. Therefore, the correct description of a carbocation is one that accurately reflects its positive charge on a carbon atom.