Which shall be burn completely to CO2 and water in the presence of sufficient amount of oxygen gas?
A. Pentane
B. Dimethylpropane
C. 2,2 dimethylpropane
D. All of the above
To determine which compound will completely burn to CO2 and water in the presence of sufficient oxygen gas, we need to consider their molecular structures.
The complete combustion of a hydrocarbon produces carbon dioxide (CO2) and water (H2O).
Let's examine each compound:
A. Pentane (C5H12) has the molecular structure CH3(CH2)3CH3.
B. Dimethylpropane (C4H10) also known as isobutane, has the molecular structure (CH3)2CHCH3.
C. 2,2-dimethylpropane (C5H12) also known as neopentane, has the molecular structure (CH3)4C.
To determine if a compound will completely burn to CO2 and water, we need to check if the amount of carbon and hydrogen atoms in the compound can be balanced with the available oxygen. By balancing the equation, we can see if all the carbon and hydrogen atoms are accounted for in the products.
Let's balance the equation for each compound:
A. Pentane: C5H12 + O2 → CO2 + H2O
By balancing the equation, we find that pentane requires 8.5 molecules of oxygen for complete combustion. Since the molecular formula of oxygen is O2, we cannot have half a molecule of oxygen. Therefore, pentane cannot completely burn to CO2 and water.
B. Dimethylpropane: C4H10 + O2 → CO2 + H2O
By balancing the equation, we find that dimethylpropane requires 6 molecules of oxygen for complete combustion. Since we have O2 as the source of oxygen, we can supply 6 molecules of oxygen to achieve complete combustion of dimethylpropane.
C. 2,2-dimethylpropane (neopentane): (CH3)4C + O2 → CO2 + H2O
By balancing the equation, we find that neopentane requires 12.5 molecules of oxygen for complete combustion. Again, we cannot have a fraction of a molecule of oxygen, so neopentane cannot completely burn to CO2 and water.
Based on the analysis, only dimethylpropane (B) can completely burn to CO2 and water in the presence of sufficient oxygen gas. Therefore, the correct answer is B. Dimethylpropane.