double bonds

[Zahta]

Can someone please help me with 2009 vcca paper  question   4d  short answer.  Determine the number of double bonds in each molecule  of myrcene.  Why cant i use  the double  bond formula? Also what is the law of conservation mass.

[rebeckab]

conversation of mass is just saying that you can't lose or gain mass in a reaction, so the stuff on the left has to add up to the stuff on the right That should have been how you worked out 4c, and then from that you can work out the mole of c10H22, which will be equal to the mole of myrcene. Use that and the mass of myrcene (1.00g) to work out the molecular mass, and find out the number of hydrogens there are when there are 10 carbons. So then you can find out the number of double bonds.

Hope that makes some kind of sense, that's just how it makes sense to me haha And what's the double bond formula?

[Bhootnike]

you cant use it because you dont know the chemical formula for myrcene. you need to know the number of mole of  H2 gas that reacted with it.  - which is 3.
so myrcene is c10h16. using double bond formula, that gives you 3 double bonds.

but you needed to figure out number of mole of h2 reacting.

[Zahta]

Some cool formula i found on the atar notes study guide, i forgot what it was called.  Thanks guys