79.2 g of C14H30 is cracked to produce 40.0 g of C7H16, 17.6 g of C3H8, and 22.4 g of C2H4. Options: a) The molar mass of C14H30 is 210 g/mol. b) The cracking process is an example of a combustion reaction. c) The molar mass of C7H16 is 100 g/mol. d) The molar mass of C3H8 is 44 g/mol.
The Correct Answer and Explanation is:
The correct answer is d) The molar mass of C3H8 is 44 g/mol.
Here’s an explanation for each option:
- Option a: The molar mass of C14H30 is 210 g/mol.
- To determine the molar mass of C14H30, we add up the atomic masses of carbon and hydrogen.
- Carbon (C) has an atomic mass of 12 g/mol, and hydrogen (H) has an atomic mass of 1 g/mol.
- So, the molar mass of C14H30 is:
[
(14 \times 12) + (30 \times 1) = 168 + 30 = 198 \text{ g/mol}.
] - Since 198 g/mol is not equal to 210 g/mol, this option is incorrect.
- Option b: The cracking process is an example of a combustion reaction.
- Combustion reactions typically involve the burning of a substance with oxygen, producing carbon dioxide and water.
- Cracking, however, is a process where large hydrocarbons like C14H30 are broken down into smaller molecules (like C7H16, C3H8, and C2H4) and does not require oxygen. This makes cracking a type of decomposition reaction, not combustion. Therefore, this option is incorrect.
- Option c: The molar mass of C7H16 is 100 g/mol.
- We can calculate the molar mass of C7H16:
[
(7 \times 12) + (16 \times 1) = 84 + 16 = 100 \text{ g/mol}.
] - This is correct, but it does not relate to the other calculations in this particular question, so it’s not the answer we’re looking for.
- Option d: The molar mass of C3H8 is 44 g/mol.
- We calculate the molar mass of C3H8:
[
(3 \times 12) + (8 \times 1) = 36 + 8 = 44 \text{ g/mol}.
] - This is correct, and since the molar mass of C3H8 is directly given in the question as part of the options, this is the correct answer.
Thus, option d is the correct choice.