Alkenes (T)

• What is the general formula for alkenes?

  Alkenes have the general formula $C_nH_{2n}.$
• Why are alkenes considered unsaturated?

  Because they have two fewer hydrogen atoms than the alkane with the same number of carbon atoms.
• How do you calculate the number of hydrogen atoms in an alkene given the number of carbon atoms?

  • Multiply the number of carbon atoms (n) by 2.
• What is the molecular formula of ethene?

  The molecular formula of ethene is $C_2H_4.$
• What is the molecular formula of propene?

  The molecular formula of propene is $C_3H_6.$
• What is the molecular formula of butene if it has four carbon atoms?

  • The molecular formula of butene is $C_4H_8.$
• What is the molecular formula of pentene if it has five carbon atoms?

  • The molecular formula of pentene is $C_5H_{10}.$
• Why is the position of the double bond in alkenes not important at the GCSE level?

  Because it can be placed between any two adjacent carbon atoms.
• What is the difference in hydrogen atoms between an alkene and its corresponding alkane?

  • Alkenes have two fewer hydrogen atoms than the corresponding alkane.
• How many hydrogen atoms does ethane have?

  Ethane has six hydrogen atoms.
• How many hydrogen atoms does ethene have?

  Ethene has four hydrogen atoms.