Chemistry Help?

Question

I need some help on Chemistry, i do not understand how to do this, and really need a good grade so if someone can do it, or tell me how please do? thanks
1. write the molecular formula for the alkene hydrocarbon that contains 9 carbon atoms?
a * for alkyne that contains 7 carbon atoms?
b. alkene that has a molar mass of 42.09 grams?
c.alkyne that has a molar mass of 40.07 grams?
2. write general formula for an alkene hydrocarbon?

Answer 1

C9H18 C7H12 C3H6 C3H4 CnH2n

Answer 2

All alkenes will have the formula CnH2n. Since you have 9 carbons, you will have 18 hydrogens.

Alkynes have the formula CnH2n-2. So, with 7 carbons, you will have 12 H atoms.

For the b and c parts, you can set up a formula using the atomic mass of C and H, and the numbers of carbons and hydrogens. So, for an alkene:

12(n) + 1(2n) = 42
14n=42
n=3
Formula is C3H6

And for an alkyne
12(n) + 1(2n-2) = 40
14n-2=40
14n=42
n=3
Formula is C3H4

Answer 3

an alkene is an unsaturated chemical compound containing at least one carbon-to-carbon double bond.
general formula isC(n)H(2n).
so according to what u say,for the alkene hydrocarbon that contains 9 carbon atoms,it's
C9H18

an alkyne has at least one triple bond between two carbon atoms, with the formula C(n)H(2n-2).
so,it's C7H12


b) if we accept 1 mol C=12 gr and 1 mol H=1 gr so
12n+2n=42
n=3 so it's C3H6


c) 12n+2n-2=40
n=3 so it's C3H4

Answer 4

1. molecular formula for alkene 9 C atoms - C9H18
a. alkyne with 7 C atomsC7H12
b. alkene with 42.09g - C3H6(3*12.01)+(6*1.01)
c. alkyne with 40.07g - C3H4(3*12.01)+(4*1.01)
2. general formula for alkene - C=C

Answer 5

1.C9H18
a.C7H13
2.CnH2n(unsure bout b. n c.)