# The mass fractions of carbon and hydrogen in the composition, respectively, are: C – 69.77%, H – 11.6%.

The mass fractions of carbon and hydrogen in the composition, respectively, are: C – 69.77%, H – 11.6%. The vapor density in nitrogen is 3.072. Find the molecular formula, make up Semi-structural and name the substance.

Given:
ω (C in in-ve) = 69.77%
ω (H in in-ve) = 11.6%
D N2 (in-va) = 3.072

To find:
the formula of the island -?

Decision:
1) M (in-va) = D N2 (in-va) * M (N2) = 3.072 * 28 = 86.016 ≈ 86 g / mol;
2) Mr (in-va) = M (in-va) = 86;
3) N (C in in-ve) = (ω (C in in-ve) * Mr (in-va)) / (Ar (C) * 100%) = (69.77% * 86) / (12 * 100%) = 5;
4) N ​​(H in in-ve) = (ω (H in in-ve) * Mr (in-v)) / (Ar (H) * 100%) = (11.6% * 86) / (1 * 100%) = 10;
5) The substance contains another element / elements:
Ar (element) = Mr (in-va) – Ar (C) * N (C in v-ve) – Ar (H) * N (H in v-ve) = 86 – 12 * 5 – 1 * 10 = 16;
It can be 1 oxygen or 4 helium; only oxygen is suitable;
6) Unknown substance – C5H10O – it can be an aldehyde, ketone, unsaturated monohydric alcohol, unsaturated ether or cyclic oxide.

Answer: Unknown substance – C5H10O – aldehyde, ketone, unsaturated monohydric alcohol, unsaturated ether or cyclic oxide.

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