# In organic matter, the mass fractions of carbon, hydrogen, oxygen and nitrogen, respectively

In organic matter, the mass fractions of carbon, hydrogen, oxygen and nitrogen, respectively, are equal to 32,0,6,66,42,67,18,67%. Derive the molecular formula of a substance. What class of compounds does this substance belong to?

Given:
ω (C) = 32.0%
ω (H) = 6.66%
ω (O) = 42.67%
ω (N) = 18.67%

To find:
CxHyOzNk -?

1) Let m (CxHyOzNk) = 100 g;
2) m (C) = ω (C) * m (CxHyOzNk) / 100% = 32.0% * 100/100% = 32.0%;
3) n (C) = m (C) / M (C) = 32.0 / 12 = 2.667 mol;
4) m (H) = ω (H) * m (CxHyOzNk) / 100% = 6.66% * 100/100% = 6.66%;
5) n (H) = m (H) / M (H) = 6.66 / 1 = 6.66 mol;
6) m (O) = ω (O) * m (CxHyOzNk) / 100% = 42.67% * 100/100% = 42.67%;
7) n (O) = m (O) / M (O) = 42.67 / 16 = 2.667 mol;
8) m (N) = ω (N) * m (CxHyOzNk) / 100% = 18.67% * 100/100% = 18.67%;
9) n (N) = m (N) / M (N) = 18.67 / 14 = 1.334 mol;
10) x: y: z: k = 2.667: 6.66: 2.667: 1.334 = 2: 5: 2: 1;
11) C2H5O2N – glycine – amino acid.

Answer: The unknown substance is glycine.

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