CHEM AND BIO HELP AND TIPS HERE

[nid404]

Here is one example ...
It came as a graph in paper3 may/june 2009 Q5

this was answered somewhere before. I'll look for the explanation

[basharooo]

guys what is the big idea about MOLES , Like i study the chapter from my textbook , but when i open the
past papers i cant really solve anything .. ?
the moles are partially hard

[nid404]

nope they're the easiest part of chemistry
Just post your question here...I'll answer 'em  I have AS chem tom 

[CatAly$t]

pls,

can somebody answer for me q5 in 2002 june....

http://www.freeexampapers.us/IGCSE/Chemistry/CIE/2002%20Jun/0620_s02_qp_3.pdf

no answer on ms...i just wanna  check my answers...

thx

[nid404]

the a) part?

Liquids take the shape of the container, they maintain their volume. The intermolecular forces in liquids are significant and therefore, they do not expand to occupy all the space available (as gases do). A given mass of liquid has a fixed volume. also molecules in liquid have less k.e as compared to that of gases.Particles in gases have very weak intermolecular forces and high kinetic energy, hence the particles move independent of each other and occupy the space available to them.

[CatAly$t]

the a) part?

Liquids take the shape of the container, they maintain their volume. The intermolecular forces in liquids are significant and therefore, they do not expand to occupy all the space available (as gases do). A given mass of liquid has a fixed volume. also molecules in liquid have less k.e as compared to that of gases.Particles in gases have very weak intermolecular forces and high kinetic energy, hence the particles move independent of each other and occupy the space available to them.

thanks  ...pls try to solve for me the questions on the last page pls....if u have time 

thx

[Meticulous]

b)i) rate= time and volume. In other words, its the volume produced and the time taken.

ii) CO2 due to lower molecular mass. or less density

[CatAly$t]

b)i) rate= time and volume. In other words, its the volume produced and the time taken.

ii) CO2 due to lower molecular mass. or less density

thx...

and the last page please....i really su*k in mole calculations  ...if possible,with some explanations pls....

thx

[Ivo]

thx...

and the last page please....i really su*k in mole calculations  ...if possible,with some explanations pls....

thx

The equation you need to use is:

                      Volume of gas (in dm³)
Moles of gas = --------------------------
                                      24

Note to convert cm³ to dm³, divide quantity by 1000 (e.g. 20cm³/1000=0.02dm³)

This is the proper theory and equation behind my calculations below.

Here are the answers for 5) c) as requested:

i)   Moles of C₄H₆: 0.02/24=0.000833
     From equation, we know 2 moles of C₄H₆ reacts with 11 moles of O₂
     Therefore, moles of O₂: 0.000833*5.5=0.00458
     Therefore, volume of O₂: 4.58*24*1000=110cm³

ii)  From equation, we know 2 moles of C₄H₆ produces 8 moles of CO₂
     Therefore, moles of CO₂: 0.000833*4=0.00333
     Therefore, volume of CO₂: 0.00333*24*1000=80cm³

iii) From equation, we know 2 moles of C₄H₆ produces 6 moles of H₂O
     Therefore, moles of H₂O: 0.000833*3=0.0025
     Therefore, volume of H₂O: 0.0025*24*1000=60
     Therefore, total volume of gases is simply volume of CO₂ + volume of H₂O:
     80+60=140cm³

     Alternatively, 8+6=14, so 2 moles of C₄H₆ produces 14 moles of products
     Therefore, moles of products: 0.000833*7=0.00583
     Therefore, volume of products: 0.00583*24*1000=140cm³

For part d), you use this formula:

             Mass
Moles = ------
               M_r

d)  From the above equation, 1 mole of butyne forms 3 moles of water
     Number of moles of butyne reacted: 9/54=0.167
     Number of moles of water formed: 0.167*3=0.5
     Mass of water formed: 0.5*(2+16)=9g

I hope this has helped.

[holtadit]

@Ivo  +rep   Keep it up !

[CatAly$t]

The equation you need to use is:

                      Volume of gas (in dm³)
Moles of gas = --------------------------
                                      24

Note to convert cm³ to dm³, divide quantity by 1000 (e.g. 20cm³/1000=0.02dm³)

This is the proper theory and equation behind my calculations below.

Here are the answers for 5) c) as requested:

i)   Moles of C₄H₆: 0.02/24=0.000833
     From equation, we know 2 moles of C₄H₆ reacts with 11 moles of O₂
     Therefore, moles of O₂: 0.000833*5.5=0.00458
     Therefore, volume of O₂: 4.58*24*1000=110cm³

ii)  From equation, we know 2 moles of C₄H₆ produces 8 moles of CO₂
     Therefore, moles of CO₂: 0.000833*4=0.00333
     Therefore, volume of CO₂: 0.00333*24*1000=80cm³

iii) From equation, we know 2 moles of C₄H₆ produces 6 moles of H₂O
     Therefore, moles of H₂O: 0.000833*3=0.0025
     Therefore, volume of H₂O: 0.0025*24*1000=60
     Therefore, total volume of gases is simply volume of CO₂ + volume of H₂O:
     80+60=140cm³

     Alternatively, 8+6=14, so 2 moles of C₄H₆ produces 14 moles of products
     Therefore, moles of products: 0.000833*7=0.00583
     Therefore, volume of products: 0.00583*24*1000=140cm³

For part d), you use this formula:

             Mass
Moles = ------
               Mr

d)  From the above equation, 1 mole of butyne forms 3 moles of water
     Number of moles of butyne reacted: 9/54=0.167
     Number of moles of water formed: 0.167*3=0.5
     Mass of water formed: 0.5*(2+16)=9g

I hope this has helped.

thanks man  ....bath rocks!!!

[Helium]

Whats heated and instead of melting turns into solid?

[nid404]

huh...when you heat anything, molecules in it will always move away from each other.

[Ivo]

Whats heated and instead of melting turns into solid?

I don't get what you mean by "whats heated", and for your second question, freezing/solidification is the process of turning a liquid into a solid.

[Helium]

naah, it's just one of my friends planning to take chem next year,

so he challenged me to anwser that question, he said it's eggs, LOL

Yes i know it sounds lame , i told him a chemical reaction took place when boiling or cooking the egg,

but he still loves that question