POST YOUR BIO AND CHEM PAPER 1 DOUBT HERE !!!!

[Rania MD]

1)The pH of pure ethanol and all other alcohols is 7, because the pH refers to the number of OH- or H+ ions in a solution, neither are present in any alcohols.




2)B
3)PbO2 + 2H2O → Pb + 2H2Oin the tube lead(ii)oxide will loose the o2 & Pb will remain in tube mass decrease drying agent absorbs the water increasing in mass the answer is B
4)Firstly Zn becomes ZnO the alloy has also Cu .. Cu cant react with H2SO4 cuz it cant displace the hydrogen (less reactive) so ZnO + H2SO4àZnSO4 + H2O water is the colorless solution & zincsulfide is the brown solid answer is B
5)Q22: as previous explanation
Q33: fossil fuels are made from dead organic matter this matter can be plants ..plants contain nitrogen compounds when u burn the fossil fuels which may include dead plants NO2 if given off

6)Very simple with no complications: they gave u 2 statements
Statement 1: Alloying iron with other materials to form stainless steel prevents iron from rusting
by excluding oxygen.
Statement 2: Painting, oiling and electroplating are all methods of preventing iron from rusting.
great explanation, Good luck

The first statement is 100% WRONG because oxygen is not excluded the oxygen concentration in the surrounding is not even controlled to make an alloy . simply alloying is when 2 or more metals are mixed to make this metal mixture stronger & last a little bit longer BUT EVENTUALLY THIS ALLOY IS GOING TO RUST BY TIME the second statement is correct and therefore the answer is D

 

[Razo513]

anytime

 

[Evangeline]

I solve past papers each day, I got really bored from studying! what about u?

same i just want to take a break ! hopefully our work is fruitful

 

[L-Girl]

same i just want to take a break ! hopefully our work is fruitful

i really hope so! it's been the toughest year in my whole life!

 

[Evangeline]

i really hope so! it's been the toughest year in my whole life!

me too . required responsibility along with hard work.. a transitional phase!

 

[Evangeline]

can anyone please give me the link to chemistry paper1 markscheme year 1994 ... thanks

 

[GorgeousEyes]

What's the effect on the Ph of an acid or a base when we add water ?

 

[FATIMAH]

Assalam-o-alaikum wr wb...
the question says that the graph is for a 'single' heartbeat...so we can conclude that it takes 0.6 seconds for one heartbeat...to get the number of heartbeats in 60 seconds (1 minute) we will divide 60 by 0.6 that is equal to 100 heartbeats..!
hope that clears your doubt

thanks soo much !! i got it

 

[Tekno-M]

What's the effect on the Ph of an acid or a base when we add water ?

I think the acid/base will only become less concentrated, and I don't think concentration affects pH.

 

[GorgeousEyes]

I think the acid/base will only become less concentrated, and I don't think concentration affects pH.

There's a question in Jun03 , it's no.21 . When we added water The PH increased , but i thought that water since it's neutral doesn't effect PH .

 

[L-Girl]

There's a question in Jun03 , it's no.21 . When we added water The PH increased , but i thought that water since it's neutral doesn't effect PH .

i think because water made the acid more dilute

 

[Tekno-M]

Well in that case my info is wrong :/ The concentration actually affects the pH. My understanding is that when water is added, solution becomes more dilute, therefore, less H+ ions are released in solution, therefore more pH. (pH is the measure of the amount of H+ / OH+ ions released in solution). In other words, as an acid becomes more dilute, it becomes closer and closer to the pH of water (7).

 

[GorgeousEyes]

I think you are both right , thanks

 

[L-Girl]

I think you are both right , thanks

i love your picture of Cyrine btw

 

[L-Girl]

chem, question 10 june 2000
bio, question 37 november 2002
please help

 

[FATIMAH]

here's it

from where you got june 02 paper ????

 

[Razo513]

chem, question 10 june 2000
bio, question 37 november 2002
please help

chem question 10) B why ? because P^3- * Cl^- criss cross PCl3
bio question: 37) A why? carnivores eat other animals which may be herbivores when carnivores are removed herbivores will survive thus their number increases

 

[Razo513]

from where you got june 02 paper ????

u can get it off freeexampapers.com

 

[L-Girl]

chem question 10) B why ? because P^3- * Cl^- criss cross PCl3
bio question: 37) A why? carnivores eat other animals which may be herbivores when carnivores are removed herbivores will survive thus their number increases

thank you
but are u sure of the bio answer? because the question says which graph shows the growth of a population when there are no limiting factors!
it was repeated in nov 1999 and nov 2002, but the answers are different and i got confused

 

[Razo513]

s

thank you
but are u sure of the bio answer? because the question says which graph shows the growth of a population when there are no limiting factors!
it was repeated in nov 1999 and nov 2002, but the answers are different and i got confused

srry it's B for the same reason