Determine the molecular formula of decene, which has an empirical formula of CH2 and a molar mass of 140.27 g/mol.

Molecular formula = C₁₀H₂₀

Explanation:

Given data:

Empirical formula = CH₂

Molar mass = 140.27 g/mol

Molecular formula = ?

Solution:

Molecular formula = n (empirical formula)

n = molar mass of compound / empirical formula mass

Now we will calculate the empirical formula mass.

CH₂ = 12 × 1 + 1× 2

CH₂ = 12 +2

CH₂ = 14  

n = 140.27 / 14

n = 1 0

Molecular formula = n (empirical formula)

Molecular formula = 10 (CH₂)

Molecular formula = C₁₀H₂₀

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.