Propane (C3H8) burns according to the following balanced equation:
C3H8(g)+5O2(g)→3CO2(g)+4H2O(g)
You may want to reference (bookLink. gif pages 277 - 280) Section 6.9 while completing this problem.

Part A

Calculate ΔH∘rxn for this reaction using standard enthalpies of formation. (The standard enthalpy of formation of gaseous propane is -103.9 kJ/mol.)

Express the enthalpy in kilojoules to four significant figures.

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.

hey there!

mass = 6.75 g

volume =   9 cm³

therefore:

d = mass / volume

d   = 6.75 / 9

d = 0.7 g/cm³

answer b

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.