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The molecular formula of butene is C4H8 - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2018 - Paper 1
Question 2
The molecular formula of butene is C4H8. Which of the following is the empirical formula of butene? A CH B C2H4 C C4H8 D (CH2)4 (b) Calculate the relative for... show full transcript
Worked Solution & Example Answer:The molecular formula of butene is C4H8 - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2018 - Paper 1
Step 1
a) Which of the following is the empirical formula of butene?
Answer
The empirical formula of butene is derived from its molecular formula, C4H8. To obtain the empirical formula, divide the subscripts of the molecular formula by their greatest common divisor, which is 4 in this case:
- C: 4 ÷ 4 = 1
- H: 8 ÷ 4 = 2
Thus, the empirical formula is CH2. From the options provided, the correct answer is B: C2H4.
Step 2
b) Calculate the relative formula mass of butene, C4H8.
Answer
To calculate the relative formula mass of C4H8, we consider the atomic masses provided:
- Carbon (C) = 12
- Hydrogen (H) = 1
The formula mass calculation is as follows:
egin{align*} ext{Relative formula mass} & = (4 imes 12) + (8 imes 1) \ & = 48 + 8 \ & = 56 \ ext{Thus, the relative formula mass of butene (C4H8) is} & = 56. ext{This can also be represented as:} \ (4 imes 12) + (8 imes 1) = 56. \end{align*}
Step 3
c)(i) Balance the equation for this reaction by putting numbers in the spaces provided.
Answer
The balanced chemical equation for the combustion of butene (C4H8) in oxygen can be represented as follows:
C4H8 + 6 O2 → 4 CO2 + 4 H2O
Where:
- 6 O2 represents the six molecules of oxygen needed for complete combustion,
- The coefficients '4' before CO2 and H2O show that four molecules of carbon dioxide and four molecules of water are produced.
Step 4
c)(ii) Describe the test to show that a gas is carbon dioxide.
Answer
To test whether a gas is carbon dioxide, one can perform a simple experiment involving limewater (a dilute solution of calcium hydroxide).
- Pass the gas through limewater.
- If the gas is carbon dioxide, it will react with calcium hydroxide to form calcium carbonate, which is insoluble and causes the limewater to turn milky.
- The milky appearance indicates a positive test for carbon dioxide.