Question

Elemental analysis of caffeine yields the following results: 49.49% C, 5.15% H, 28.87% N, and the remainder is O. What is the molecular formula of caffeine?

Answer 1

The answer to your question is C₄H₅N₂O

Step-by-step explanation:

Process

1.- Calculate the percent of oxygen in the sample

Percent of oxygen = 100 - 49.49 - 5.15 - 28.87

Percent of oxygen = 16.49 %

2.- Write the percents as grams

C = 49.49 g

H = 5.15 g

N = 28.87 g

O = 16.47 g

3.- Convert the grams to moles

C 12 g ------------------- 1 mol

49.49 g ---------------- x

x = (49.49 x 1) 12

x = 4.12 moles

H 1 g ------------------- 1 mol

5.15 g ---------------- x

x = (5.15 x 1)/ 1

x = 5.15 moles

N 14 g --------------- 1 mol

28.87 g ---------- x

x = (28.87 x 1) / 14

x = 2 mol

O 16 g ---------------- 1 mol

16.49 g ----------- x

x = (16.49 x 1) / 16

x = 1.03 moles

4.- Divide by the lowest number of moles

C 4.12 / 1.03 = 4

H 5.15 / 1.03 = 5

N 2 / 1.03 = 1.9 ≈ 2

O 1.03 / 1.03 = 1

5.- Write the empirical formula

C₄H₅N₂O