chemistry questions...?

Question

1. Cholesterol, an important steroid found in nearly all human body tissue, contains 84.0% carbon by weight. If cholesterol has a molecular weight of 386, how many carbon atoms are there in each molecule of cholesterol?
a) 7
b) 14
c) 27
d) 32
e) 64

2. In sodium hydroxide, the percentage of oxygen by mass is nearest to
a) 20%
b) 40%
c) 60%
d) 80%
e) 90%

3. Which one of the following formulas is an empirical one?
a) C3H8
b) HCOOCH3
c) H2C2O4
d) CH3COOH
e) C6H6

4. Cyclohexane molecules contain only carbon and hydrogen. If there are twice as many hydrogen atoms as carbon, and cyclohexane has a molar mass of 84g, what is its true formula?
a) C5H24
b) C12H6
c) C8H4
d) CH2
e) C6H12

Thankyou for helping. Please be 100% certain of your answers. If possible please explain why it is those particular answers for each of the questions.

I just need some help! I have done most of these questions, I just need to be sure of the answers. I am a very hard working student thankyou very much!!!(1st answerer!)

Answer 1

1)
100 : 84 = 386 : x
x = 324 g of C (MM=12)
324/12 = 27 moles of C
One mole contains 6.02 10^23 atoms we have
(6.02 10^23)(27)=1.63 10^25 atoms

2)MM NaOH = 40 g/mol
Since in 40 g there are 23 g of Na
16 : 40 = x : 100
x = 40%

4)the answer is e)

Answer 2

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