A laboratory analysis of an unknown sample yields 74.0% carbon, 7.4% hydrogen, 8.6% nitrogen, and 10.0% oxygen. What is the empirical formula of the sample? Give your answer in the form C#H#N#O# where the number following the element's symbol corresponds to the subscript in the formula. (Don't include a 1 subscript explicitly). For example, the formula CH 22 O would be entered as CH2O.

Question

Atkinson

Chemistry

5 August, 09:31

A laboratory analysis of an unknown sample yields 74.0% carbon, 7.4% hydrogen, 8.6% nitrogen, and 10.0% oxygen. What is the empirical formula of the sample? Give your answer in the form C#H#N#O# where the number following the element's symbol corresponds to the subscript in the formula. (Don't include a 1 subscript explicitly). For example, the formula CH 22 O would be entered as CH2O.

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Friendo · Answer 1

Let us assume that there is a 100g sample present. The respective mass of each element will then be:

C: 74 g

H: 7.4 g

N: 8.6 g

O: 10 g

Now, we divide each constituent's mass by its Mr to obtain the moles of each

C: (74 / 12) = 6.17

H: (7.4 / 1) = 7.4

N: (8.6 / 14) = 0.61

O: (10 / 16) = 0.625

Dividing by the smallest number:

C: 10

H: 12

N: 1

O: 1

Thus, the empirical formula is

C10H12NO