A compound has an empirical formula of CHBr2. If it’s molar mass is 345.6 grams, what is it’s molecular formula

The molecular formula is C2H2Br4

Explanation:

Molar Mass of CHBr2 = 12 + 1 + (2x80) = 12 + 1 + 160 = 173

The molecular formula = n x empirical formula

Molar Mass of the compound = 345.6

Empirical formula = CHBr2

n(CHBr2) = 345.6

n x 173 = 345.6

n = 345.6/173 = 2

Therefore the molecular formula is n(CHBr2) = 2(CHBr2) = C2H2Br4

there are two significant figures.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol