Which chemical equation shows the incomplete combustion of methane? a. c3h8 + 5o2 → 3co2 + 4h2o b. 2ch4 + 3o2 → 2co + 4h2o c. ch4 + 2o2 → co2 + 2h2o

Combustion is a chemical reaction in which a hydrocarbon reacts with oxygen to form carbon dioxide (CO2) and water (H2O). In other words, all the carbons get converted to CO2 while all the hydrogens get converted into H2O.

Incomplete combustion however, results in the formation of carbon monoxide (CO) and H2O.

Methane is a hydrocarbon with a molecular formula CH4. Thus complete combustion of methane can be expressed as-

CH4 + 2O2 → CO2 + 2H2O

Ans (C)

Answer : The incomplete combustion equation of methane is, (B)

Explanation :

Combustion reaction : It is defined as the reaction in which a hydrocarbon react with oxygen to give carbon dioxide and water as a product.

As per question, the combustion of methane (a hydrocarbon) also gives carbon dioxide and water as a product.

The balanced combustion reaction of methane will be,

By the stoichiometry we can say that, 1 mole of methane react with 2 moles of oxygen to give 1 mole of carbon dioxide and 2 moles of water.

So, option (B) is an incomplete combustion reaction of methane and option (A) is the balanced combustion reaction of pentane.

Hence, the incomplete combustion equation of methane is, (B)

the missing options are :

(1) lower boiling point and a lower freezing point(2) lower boiling point and a higher freezing point(3) higher boiling point and a lower freezing point(4) higher boiling point and a higher freezing point

answer : the correct answer is option (3) higher boiling point and a lower freezing point

explanation :

when a non volatile solute is added to a solvent like water, it results in elevation of boiling point.

let us find the increase in boiling point of water when cacl₂ is added to water to make a solution of 1 m

step 1 : find molality of the solution

let us assume we have 1 l of solution.

let us convert this to grams of cacl₂.

molar mass of cacl2 is 111 g/mol

grams of cacl₂ =

mass of solute = 111 g

assuming density of solution same as water which is 1g/ml we have ,

mass of solution = density * volume

mass of solution =

mass of solution = mass of solvent + mass of solute

mass of solute = 1000g - 111g

mass of solute 889 g = 0.889 kg

the molality of the solution can be calculated as

molality = 1.12 m

step 2 : find boiling point elevation.

the elevation in boiling point is calculated as

here δtb = boiling point elevation

i = vant hoff factor which is the number of ions formed by the solute .

cacl₂ dissociates as

it forms 3 ions . therefore,

i = 3

m = molality which is 1.12 m

kb is constant for a given solvent. for water it is 0.512

the boiling point of water increases by 1.7 °c

step 3: find freezing point depression.

when a non volatile solute is added to water, it results in decrease in freezing point.

the formula to find freezing point depression is

kf is constant for water and its value is 1.86

the freezing point of water decreases by 6.2 °c

therefore we can say that, the solution will have a higher boiling point and a lower freezing point