Question

Caffeine is a compound found in some natural coffees and teas and in some colas. a. Determine the empirical formula for caffeine, using the following composition of a 100.00-g sample. 49.47 grams of carbon, 28.85 grams of nitrogen, 16.48 grams of oxygen, and 5.20 grams of hydrogen b. If the molar mass of caffeine is 194.19 g/mol, calculate its molecular formula.

Answer 1

Answer: The molecular formula will be

Step-by-step explanation:

Mass of C= 49.47 g

Mass of N = 28.85 g

Mass of O = 16.48 g

Mass of H = 5.20 g

Step 1 : convert given masses into moles.

Moles of C =

Moles of N =

Moles of O =

Moles of H =

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For C =

For N =

For O =

For H =

The ratio of C : N: O: H = 4: 2: 1: 5

Hence the empirical formula is

The empirical weight of
= 4(12)+2(14)+1(16)+5(1)= 97 g.

The molecular weight = 194.19 g/mole

Now we have to calculate the molecular formula.

The molecular formula will be =