How do you work out Q 15, 16 and 18 in 2003 in multiple choice?

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# 2003 - Multiple Choice - Q15,Q16,Q18

Started by AM4R, May 26 2006 01:46 PM

5 replies to this topic

### #1

Posted 26 May 2006 - 01:46 PM

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### #2

Posted 26 May 2006 - 01:58 PM

**Question 15**It's the number of molecules in one mole

2g of H is 1 mole

Answer:

**C**

**Question 16**write the balanced equation

2C H + 13O ------------> 8CO + 10H O

1litre C4H10 needs 6.5 litres O

Answer:

**C**

**Question 18**I don't know a logical way to do this

so i divided each mass number by 12

so for example the first one is 44, 44/ 12 = 3.7 so that means there are 3 Carbon atoms and 44-(3x12) Hydrogens = 8 Hydrogens

* 3 x 12 is the mass of the carbon atoms !!*

A formula = C3 H8

B formula = C5 H12

C formula = C6 H12

D formula = C7 H16

from this we can see A, B and D are alkanes and C is an alkene

Therefore C is from a different homologous series !!

Answer:

**C**

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### #3

Posted 26 May 2006 - 01:59 PM

For 15 you need to work out how many moles of each first.

e.g. in carbon moles is 24/12 = 2 moles. The atoms is moles x L =2L

in oxygen the moles is 0.5, and this is molecules so x L = 0.5L

in hydrogen 2/2 = 1 mole. This is molecules to just x by L = 1L

in NaCl moles is 1 x 1. And this is ions, so needs to be x by 2 as well. so its 2L

hence the answer is C!

e.g. in carbon moles is 24/12 = 2 moles. The atoms is moles x L =2L

in oxygen the moles is 0.5, and this is molecules so x L = 0.5L

in hydrogen 2/2 = 1 mole. This is molecules to just x by L = 1L

in NaCl moles is 1 x 1. And this is ions, so needs to be x by 2 as well. so its 2L

hence the answer is C!

### #4

Posted 26 May 2006 - 02:00 PM

15. Avogadros constant = 6.02x10^23. Work through each one until you find the answer C.

16. Write a balanced eq:

C4H10 + 13/2O2 ------> 4CO2 + 5H20

1 volume ----->13/2 volumes

1 litre -------> 6.5 litres

18.Draw out each molecule and see which can be drawn in more than one way. Answer A

16. Write a balanced eq:

C4H10 + 13/2O2 ------> 4CO2 + 5H20

1 volume ----->13/2 volumes

1 litre -------> 6.5 litres

18.Draw out each molecule and see which can be drawn in more than one way. Answer A

### #5

Posted 26 May 2006 - 02:14 PM

18.Draw out each molecule and see which can be drawn in more than one way. Answer A

18 is C I think, you must have read the answers wrong !!

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