Physics, Chemistry and Biology: Post your doubts here!

[Yasir Ammar]

Which year is this? n wat r the options?

It was on Oct/Nov 2007 Question #11
Options
A - C5H11OH
B- C6H9OH
C- C6 H11OH
D- C6H12

 

[kainat husain]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s06_qp_1.pdf
q- 19 wht the answe is C please explain
q-11 how to do this one the answer is C
q-9 y the answer is C :/
PLEASE HELP

 

[thats_me]

It was on Oct/Nov 2007 Question #11
Options
A - C5H11OH
B- C6H9OH
C- C6 H11OH
D- C6H12

Okie here..
So lets start with the first one:
C5H11OH + 8O2 ----> 5CO2 + 3H2O ( as in the reactant side there are 5 carbon ,so we need to place 5 before carbon in the product side also)
When trying to balance you cannot as there is 12 H so it cannot be possible..
the second one:
C6H9OH + 8O2 ---> 6CO2 + 5H2O (place 6 before the carbon in the product side to balance carbon , then balance H)
and the reaction balances so the answer is 2

 

[thats_me]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s06_qp_1.pdf
q- 19 wht the answe is C please explain
q-11 how to do this one the answer is C
q-9 y the answer is C :/
PLEASE HELP

Here..
9 : By showing two atoms together they are representing diatomic elements ,the third one is definately oxygen as it has double bond and is diatomic & the second one is hydrogen so water has both of them H2 and O2.
11: This is because in electrplating the positive electrode should have the metal with which it is plated.
19: Well, Copper being lower in reactivity series than hydrogen cannot displace it but its hydroxide and carbonate will react..

 

[sweetsis]

anyone?

cant u write the question here and state what exactly u don't get...

 

[joulie]

biology doubt:-
paper 1 2002 november question 12
what are the features of a xylem vessel. answer in markscheme is thich side walls and end walls absent.
however in my notes in xylem features i have it thick walls and end walls present

 

[Skynox]

biology doubt:-
paper 1 2002 november question 12
what are the features of a xylem vessel. answer in markscheme is thich side walls and end walls absent.
however in my notes in xylem features i have it thick walls and end walls present

Xylem has no end walls so that many tubes are arranged end-to-end forming a continous tube. And it has thick walls strenghthened by lignin..Thick lignified cell walls

 

[MERIHAN]

what is the difference b/w the two question ? i means the statement "until the green leaves have appeared above the soil " means same as "until the seedling start to photosynthesize " ISNT'D ??? THEN WHY ANSWERS DIFFERENT ???
THANKS IN ADVANCE !!

 

[Abu mota]

may/june 2009 and Q.16 dont understand it :/
Link:http://78.159.163.29:9204/745DAE5D2...bridge IGCSE/Biology (0610)/0610_s09_qp_1.pdf

 

[Abu mota]

View attachment 12075 what is the difference b/w the two question ? i means the statement "until the green leaves have appeared above the soil " means same as "until the seedling start to photosynthesize " ISNT'D ??? THEN WHY ANSWERS DIFFERENT ???
THANKS IN ADVANCE !!

Look at the graph, one says the number of cells and the other shows the dry mass. the rest is obvious i think but if u dont know still ask

 

[thats_me]

may/june 2009 and Q.16 dont understand it :/
Link:http://78.159.163.29:9204/745DAE5D2A141ADFF3D88BDA985A11CD0A539295405AB2A5CCD30BA42373DE050888461646F337B2E2BEE7400/www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s09_qp_1.pdf

From where does water leave the plant? Stomata! in the form of water vapour so it's B

 

[Ahmed Khider]

View attachment 12075 what is the difference b/w the two question ? i means the statement "until the green leaves have appeared above the soil " means same as "until the seedling start to photosynthesize " ISNT'D ??? THEN WHY ANSWERS DIFFERENT ???
THANKS IN ADVANCE !!

WOW im impressed! U look like an A* student to notice such a similarity . In q30 consider the cells as leaves, when germination starts the no of keaves remains constant and when photosynthesis starts more starch is produced and therefore the no of leaves increases. In q31 the dry mass decreases first as food is being assimilated from the cotyledons while after photosynthesis more starch is produced so the dry mass increases. P.s: Dry mass is unlike the no of cells dont get confused .

 

[Skynox]

may/june 2009 and Q.16 dont understand it :/
Link:http://78.159.163.29:9204/745DAE5D2A141ADFF3D88BDA985A11CD0A539295405AB2A5CCD30BA42373DE050888461646F337B2E2BEE7400/www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s09_qp_1.pdf

The stomata is the only place where the water moves downwards (out of the leaf)...The xylem water moves up and down and phloem doesn't contain water while the root cells carry water upwards..

 

[MERIHAN]

WOW im impressed! U look like an A* student to notice such a similarity . In q30 consider the cells as leaves, when germination starts the no of keaves remains constant and when photosynthesis starts more starch is produced and therefore the no of leaves increases. In q31 the dry mass decreases first as food is being assimilated from the cotyledons while after photosynthesis more starch is produced so the dry mass increases. P.s: Dry mass is unlike the no of cells dont get confused .

THANK YOU !! ACTUALLY I WAS TIRED AT THIS TYME AND DIDNT NOTICE THE Y AXIS !!! I HATE WHEN I DO SUCH SILLY MISTAKES !! THANKS GOT IT

 

[Ahmed Khider]

Guys could anyone help with these questions in chemistry paper 1 may-june 2007>>>>Questions 3,6&18? Thx in advance

 

[Ahmed Khider]

THANK YOU !! ACTUALLY I WAS TIRED AT THIS TYME AND DIDNT NOTICE THE Y AXIS !!! I HATE WHEN I DO SUCH SILLY MISTAKES !! THANKS GOT IT

Ur welcome . Make sure u dont make these type of mistakes in the exam..they can be costly

 

[Abu mota]

Guys could anyone help with these questions in chemistry paper 1 may-june 2007>>>>Questions 3,6&18? Thx in advance

for 3 ask that's me she will explain it alot better than me
for 6 it asks for what must occur and so it is B as all of the atoms have the same number of electrons on the first shell, the rest it can be true and can also be false.
for 18 u need to memorize than zinc dissolves in both and so it is A

 

[MERIHAN]

Ur welcome . Make sure u dont make these type of mistakes in the exam..they can be costly

INSHALLAH

 

[Ahmed Khider]

for 3 ask that's me she will explain it alot better than me
for 6 it asks for what must occur and so it is B as all of the atoms have the same number of electrons on the first shell, the rest it can be true and can also be false.
for 18 u need to memorize than zinc dissolves in both and so it is A

Thx alot ..If u dnt mind in w02 paper 1 chemistry could u explain questions 24,25 n 30??

 

[joulie]

plz help biology paper 1 2008 november question 39
how come the answer is "A" i mean 650 multiply by 5 =3250 which is less than "D" THAT IS 420 multiplied by 43 = 18060 so doesnt that cause more pollution also
question 3 i thought the answer is plant Q bcause in the drwaing the flower has only four stamens righ? and question 29
didn't the camel gain "fresh mass" because of the water so it has grown so why is the answe no growth occured?