Biology; Chemistry; Physics: Post your doubts here!

[jahanzebrockstar]

Once the pollen tube successfully attains an ovule, it delivers the two sperm cells with a burst. (wikipedia)

Plz tell the answe for the graph question in which shape of the curve

 

[Umaima]

your teacher is soo wrong there. It can be 1,2 or 2,3 or 1,3. It just depends on which readings give you best result.

No..in an old paper question.. All values differed by 0.2 ....in that we took the last two readings...not the first one...

 

[muaz_ali]

GUYS GUYS GUYS. How to make Ionic equations, gimme detailed answer. Alpha Destro.

 

[mona qureshi]

Question 19

A as 2 soluble salt or one soluble salt with acid can be used to make insoluble salt

 

[Rizwan Javed]

No..in an old paper question.. All values differed by 0.2 ....in that we took the last two readings...not the first one...

tell me the paper. It can;t happen. I have solved all the papers, and it never happened. again confirm this plz, because your misconception may distract many.

 

[Rizwan Javed]

GUYS GUYS GUYS. How to make Ionic equations, gimme detailed answer. Alpha Destro.

It's very simple. just cancel out the spectator ions and you''ll have your ionic equations.

 

[muaz_ali]

It's very simple. just cancel out the spectator ions and you''ll have your ionic equations.

I figured it out. Thanks. And how are parchy going on.?

 

[Hassan1233]

Can anyone do part d(ii) of May/June 2012 variant 21 for me?? Please

 

[Hassan Mirza Aziz]

Does anyone have any idea about what practical is going to come in physics p33? Pls share if you have some idea.

 

[Rizwan Javed]

Can anyone do part d(ii) of May/June 2012 variant 21 for me?? Please

Of which subject, and which question?

 

[Alpha Destro]

Anybody explain how to make paralellogram diaagrams with vectors?

Dont go for parllelogram diagrams they are waste of time tip to tail method is simpler and quicker saves more time in papers + you are liable to make more mistakes in the parallelogram method.

 

[Hassan1233]

Of which subject, and which question?

Oh sorry. Chemistery B8 d(ii) May-june 2012

 

[Alpha Destro]

Oh sorry. Chemistery B8 d(ii) May-june 2012

2500dm3 of O2 = 2500/24 = 104.17 moles of O2
According to equation ;
1 mole of O2 is produced by 2 moles of H2O
Hence 104.2 moles of O2 is produced by: 104.17 x 2 = 2o8.34 moles of H2O
Since no.moles = mass / Mr >>>> Mass = no.moles x Mr
thus mass of H20 required to produce 2500dm3 ( 104.17 moles) of O2 = 208.34 x 18 = 3750.12 // 3750 grams of water

 

[Rizwan Javed]

Oh sorry. Chemistery B8 d(ii) May-june 2012

First calculate the moles of Oxygen:
n=2500/24= 104.17 moles

Now according to the equation which is given earlier in the question, see the mole ratio of Oxygen to water:
According to the equation 2 moles of water produce 1 mole oxygen, so 104.17 moles of oxygen will be produced by (2*104.17) moles of water.

Therefore mass of water will be:

mass of water= moles*Mr = (2*104.17)*18 = 3750g

 

[Alpha Destro]

What does a catalytic coverter do ? plz explain with detail.

 

[Hassan1233]

What does a catalytic coverter do ? plz explain with detail.

Catalytic Converter converts harmfull gases (NO,CO,HC) into harmless gases
2NO + 2CO ----> 2CO2 +N2
2CO + O2 -----> 2CO2
HC + O2 ------>3CO2 +H2O

Reaction takes place at 500-800c.Steel helps to maintain this temp.
They are lined with Pd,Rh (Catayst)

 

[Netherdrake]

What does a catalytic coverter do ? plz explain with detail.

A catalytic converter turns harmful gases into harmless gases. For example, Catalytic converters are used in Cars. Cars throw out Carbon Monoxide and Nitrogen Dioxide. Both of these gases are harmful.

Catalytic converter oxidises Carbon Monoxide to Carbon Dioxide
And
Reduces Nitrogen Dioxide to Nitrogen thus making these both gases harmless.

 

[Hassan1233]

View attachment 53809

First calculate the moles of Oxygen:
n=2500/24= 104.17 moles

Now according to the equation which is given earlier in the question, see the mole ratio of Oxygen to water:
View attachment 53810 According to the equation 2 moles of water produce 1 mole oxygen, so 104.17 moles of oxygen will be produced by (2*104.17) moles of water.

Therefore mass of water will be:

mass of water= moles*Mr = (2*104.17)*18 = 3750g

Thankyou soo much!

 

[Hassan1233]

2500dm3 of O2 = 2500/24 = 104.17 moles of O2
According to equation ;
1 mole of O2 is produced by 2 moles of H2O
Hence 104.2 moles of O2 is produced by: 104.17 x 2 = 2o8.34 moles of H2O
Since no.moles = mass / Mr >>>> Mass = no.moles x Mr
thus mass of H20 required to produce 2500dm3 ( 104.17 moles) of O2 = 208.34 x 18 = 3750.12 // 3750 grams of water

Thankyou soo much!

 

[Netherdrake]

Can someone check out Chemistry D05/P2/Q.9
It is really difficult :O