In the formula for carbon tetrahydride, ch4, the percent composition of all elements is:

75% c, 25% h

25% c, 75% h

81% c, 19% h

20% c, 80% h

The percentage composition if carbon tetrahydride is 75% of carbon and 25% of hydrogen.

Explanation:

Molecular mass of carbon tetrahydride = 16 g/mol

Atomic mass of carbon = 12 g/mol

Atomic mass of hydrogen atom = 1 g/mol

Percentage of an element in a compound:

Percentage of carbon:

Percentage of hydrogen:

The percentage composition if carbon tetrahydride is 75% of carbon and 25% of hydrogen.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.