Question

determina formula moleculara a alchenei daca pentru reactionarea completa a unei probe cu masa de 8,4g s-au consumat 800g de apa de brom, partea de masa 4%​

Answer 1

Răspuns:

alchena  CnH2n,   are masa molara  miu=12n+2n=14n

-calculez masa de brom din solutie

ms= 800g   c= 4%

c=mdx100/ms---> md-=.4x800/100g=32gBr2

-calculez nr.moli brom,stiind miu=160g/mol

niu=m/miu=32/160mol=0,2mol Br2

-deduc nr.moli alchena,pe baza ecuatiei

1mol...........1mol

CnH2n+ Br2----> CnH2nBr2

x,,,,,,,,,,,,,,,,,,,,0,2mol

x= niu=0,2mol CnH2n

-deduc alchena

niu= m/miu---> miu= m/niu=8,4/0,2g/mol=42g/mol

14n=42---> n=3---> CH2=CH-CH3  PROPENA

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