6 The partial oxidation of butane in the presence of a catalyst has been investigated as a possible source of hydrogen.
C4H10(g) + 2O2(g) → 4CO(g) + 5H2(g)
(a) What is the most significant hazard associated with the pollutant CO(g)?
(1)
A it is a major contributor to the formation of acid rain
B it strongly absorbs infrared radiation
C it is toxic at low concentrations
D it is the main cause of ozone layer depletion
ANSWER
C - it is toxic at low concentrations
Analysis of Option/Explanation
Carbon monoxide is harmful because it binds to hemoglobin in the blood, reducing the ability of blood to carry oxygen. This interferes with oxygen delivery to the body's organs. The most common effects of CO exposure are fatigue, headaches, confusion, and dizziness due to inadequate oxygen delivery to the brain. Hence, option “C” reflects the most significant hazard.
(b) A mixture of 40cm3 of butane and 20cm3 of oxygen reacts in a sealed system to form carbon monoxide and hydrogen.
What is the total volume of gas in the system at the end of the reaction, in cm3?
(1)
A 30
B 60
C 90
D 120
ANSWER
D 120
Analysis of Option/Explanation
In order to understand the question first of all we look into balanced equation and identify moles, so we get as under;
C4H10 + 2O2→4CO2 + 5H2O
1 mole 2 moles 4 moles 5 moles
When comparing butane and oxygen, it is clear that 1 mole of butane react with 2 moles of oxygen, therefore as per given volume in the question, 20cm3 of oxygen reacts with10 moles of butane and so the excess volume of butane remaining (unreacted) is 30cm3 i.e.(40cm3-10cm3).
Since oxygen is the limiting reactant therefore we will compare the produced gasses moles with oxygen (limiting reactant), therefore;
2 moles of Oxygen produces 4 moles of CO2, hence for 20 cm3 of oxygen produces 40cm3 of CO2.
Similarly, 2 moles of oxygen produces 5 moles of water, hence for 20 cm3 of oxygen produces 50 cm3
Therefore, making a total of volume of gasses at the end of reaction
