Biology; Chemistry; Physics: Post your doubts here!

[Vogue]

i saw a bio experiment
it is abt finding out whether carbon dioxide is given off during fermentation
it goes lyk dis:
add few grains of yeast to distilled water. stir
after 20 min add eq vol of glucose to yeast suspension. add a litle oil on top of it
the question is that wat does the layer of oil serve as?

 

[Fallen316]

i saw a bio experiment
it is abt finding out whether carbon dioxide is given off during fermentation
it goes lyk dis:
add few grains of yeast to distilled water. stir
after 20 min add eq vol of glucose to yeast suspension. add a litle oil on top of it
the question is that wat does the layer of oil serve as?

it acts as a barrier , prevents air/oxygen to enter the flask/beaker/watever it is.
because for fermentation , no oxygen should be present

 

[ayeshaK]

i saw a bio experiment
it is abt finding out whether carbon dioxide is given off during fermentation
it goes lyk dis:
add few grains of yeast to distilled water. stir
after 20 min add eq vol of glucose to yeast suspension. add a litle oil on top of it
the question is that wat does the layer of oil serve as?

Yeast should respire anaerobically so the oil prevents oxygen from entering the experiment !!

 

[Vogue]

it acts as a barrier , prevents air/oxygen to enter the flask/beaker/watever it is.
because for fermentation , no oxygen should be present

but then how wud carbon dioxide will be distinguished cz they were connecting that test tube wid another one that contained limewater so obviosly wen CO2 will make it abv the oil nd reach till the next tube, only den it will b made sure that CO2 has evolved?

 

[Fallen316]

but then how wud carbon dioxide will be distinguished cz they were connecting that test tube wid another one that contained limewater so obviosly wen CO2 will make it abv the oil nd reach till the next tube, only den it will b made sure that CO2 has evolved?

lol , use your mind .. CO2 can pass through the connecting tube because it is inserted INSIDE the test tube containing the suspension .. got it ?

 

[Dukeofwin]

the dependent value comes on Y-axis and the Independent value comes on x-axis

Thank you

 

[ayeshaK]

lol , use your mind .. CO2 can pass through the connecting tube because it is inserted INSIDE the test tube containing the suspension .. got it ?

http://www.google.com.pk/search?um=...2.2.0.0.0.0.255.505.2-2.2.0...0.0.O8QGHZOSR6s
The first picture in this link !! Wht in this case ? Can co2 diffuse thru oil ?

 

[sweetiepie]

http://www.xtremepapers.com/community/threads/my-notes-links-on-xpc.14795/ HELPFUL WAY TO FIND NOTES

 

[Fallen316]

http://www.google.com.pk/search?um=1&hl=en&client=safari&tbo=d&biw=768&bih=928&tbm=isch&sa=1&q=yeast fermentation apparatus&oq=yeast fermentation a&aq=0&aqi=g1g-S9&aql=&gs_l=img.1.0.0j0i24l9.7746.8094.0.9703.2.2.0.0.0.0.255.505.2-2.2.0...0.0.O8QGHZOSR6s
The first picture in this link !! Wht in this case ? Can co2 diffuse thru oil ?

i dont know the reason why , but yes .
otherwise all the experiments would give a negative result :/

 

[asd]

http://www.google.com.pk/search?um=1&hl=en&client=safari&tbo=d&biw=768&bih=928&tbm=isch&sa=1&q=yeast fermentation apparatus&oq=yeast fermentation a&aq=0&aqi=g1g-S9&aql=&gs_l=img.1.0.0j0i24l9.7746.8094.0.9703.2.2.0.0.0.0.255.505.2-2.2.0...0.0.O8QGHZOSR6s
The first picture in this link !! Wht in this case ? Can co2 diffuse thru oil ?

During anaerobic respiration, bubbles are produced which when burst give off CO2. So CO2 then can easily go through the tube to lime water and turn it milky.

 

[asd]

they come out from the same part...

This is totally shit, I've seen pictures-some show they come out from the same point on the testa, while others show that plumule grow out from the top, and radicle from the bottom/middle of the testa.

 

[areeba fatima]

Thank you

my pleasure! btw welcome

 

[scouserlfc]

This is totally shit, I've seen pictures-some show they come out from the same point on the testa, while others show that plumule grow out from the top, and radicle from the bottom/middle of the testa.

And then i think the pictures were misleading because both do come from the same point and if u have done MCQs and Theory papers u will know for urself that it comes from the same place

If u want a proof ill tell u the papers year !

 

[Talhakhan]

http://www.xtremepapers.com/papers/...tional O Level/Biology (5090)/5090_y12_sy.pdf
Heading 5.5 !
There are no specific notes for the atp but u have to attempt past papers !! And practice graphs and magnification !!
And yes revise all kinds of experiments and specially the food tests !! Eg iodine test etc !

Thank u for ur help......

 

[hafsaaamer]

hey guys i need ur help !!!! can any1 tell me where can we find specimen papers ??? can some one please post the link i cant find it :/ i will be watng

 

[Fallen316]

hey guys i need ur help !!!! can any1 tell me where can we find specimen papers ??? can some one please post the link i cant find it :/ i will be watng

i guess there are none ... the paper pattern hasn't changed for like 15-30 years i think. and neither will
even if there are any they would be really old and impossible to find.

 

[selgomez]

Q.5 An experiment was carried out to measure the rate of reaction between excess powdered calcium carbonate and dilute acids.
(a) In Experiment 1, 25 cm3 of 1.5 mol/dm3 hydrochloric acid was used. Complete the equation for the reaction by filling in the missing state symbols.

(i) 2HCl(……..) + CaCO3(……..) → CaCl2(aq) + H2O (……..) + CO2(……..)

(ii) Calculate the total volume of carbon dioxide that is made from this reaction at r.t.p.

Help needed with (a)(ii)!!!!!!!!

 

[SalmanPakRocks]

Q.5 An experiment was carried out to measure the rate of reaction between excess powdered calcium carbonate and dilute acids.
(a) In Experiment 1, 25 cm3 of 1.5 mol/dm3 hydrochloric acid was used. Complete the equation for the reaction by filling in the missing state symbols.

(i) 2HCl(……..) + CaCO3(……..) → CaCl2(aq) + H2O (……..) + CO2(……..)

(ii) Calculate the total volume of carbon dioxide that is made from this reaction at r.t.p.

Help needed with (a)(ii)!!!!!!!!

(i) 2HCl (aq) + CaCO3 (s) → CaCl2(aq) + H2O (l) + CO2 (g)

(ii) no. of moles of HCL = 1.5 * 25/1000 = 0.0375 mol
2 : 1
0.0375: x
2x = 0.0375
x = 0.01875 * 24 = 0.45 dm^3

 

[Mayedah]

Q.5 An experiment was carried out to measure the rate of reaction between excess powdered calcium carbonate and dilute acids.
(a) In Experiment 1, 25 cm3 of 1.5 mol/dm3 hydrochloric acid was used. Complete the equation for the reaction by filling in the missing state symbols.

(i) 2HCl(……..) + CaCO3(……..) → CaCl2(aq) + H2O (……..) + CO2(……..)

(ii) Calculate the total volume of carbon dioxide that is made from this reaction at r.t.p.

Help needed with (a)(ii)!!!!!!!!

Multiply 25 with 1.5 =37.5
Now divide the answer by 1000
It will be 0.0375
Now from the equation u can see tht 2 moles of hcl react with one mole of carbondioxide so divide answer by 2
0.0375/2=0.01875
Now mltiply this answer with 24 to find volume
0.01875x24= 0.45

 

[SalmanPakRocks]

Multiply 25 with 1.5 =37.5
Now divide the answer by 1000
It will be 0.0375
Now from the equation u can see tht 2 moles of hcl react with one mole of carbondioxide so divide answer by 2
0.0375/2=0.01875
Now mltiply this answer with 24 to find volume
0.01875x24= 0.45

Your late Haha