We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
Click here to Donate Now (View Announcement)
U can find it over here:adnanj said:plz help draw the graph of q2c
http://www.xtremepapers.me/CIE/Cambridg ... _qp_42.pdf
Got it.....thnx...Soulgamer said:Its easier if you make a tangent where the line hits the circle and make a normal perpendicular to the (line) tangent.
Yeah remove it..... :xSAUD ASLAM said:Not Block it ,ReMOvE IT =@ =@ 8)
abcde said:May help candidates appearing in November or later so ease up on the anger!
hahaha...it was me with mad emotion...i m happy bt i don't want to recall the papers i hv given thats y...so yes we can leave it open for other students...abcde said:So am I. But I saw the 'mad' emoticon somewhere
Tips on testing for Reducing Sugar/lipids/Protein/Starch
Starch:
Crush and grind a given solid sample
either you can make a solution with this or you can directly proceed to adding Iodine solution
Place the sample on a WHITE TILE (important!!)
Add Iodine SOLUTION (iodine disqualifies, it should be iodine solution)
Colour change:
red brown to blue black if starch is present
Reducing sugars:
Always for solutions only
If solid sample, crush and grind add 2cm3 of water and make a solution
Add equal amounts of Benedicts solution(if you have a 2cm3 solution, you have to add 2cm3 of benedicts )
HEAT over a WATER BATH
Colour change if reducing sugar is present:
blue to green/yellow/orange if only a little concentration of reducing sugar present in test solution
otherwise it is blue to BRICK RED PRECIPITATE!!
Proteins:
Add 2cm of Sodium/Potassium Hydroxide solution into the sample
Add a few drops of Copper sulphate solution using a pipette into the test tube containing the sample
If proteins are present:
Colour change is blue(due to Copper sulphate) to purple/mauve/lilac!
Lipids:
If it is a DRY solid, crush and grind the sample
Place it in a DRY test tube (have to be dry otherwise the experiment will be inaccurate)
add about 2cm3 of ethanol to the test tube containing the dry sample
pour ONLY THE LIQUID PART OF THE SAMPLE SOLUTION containing ethanol into another test tube containing 2cm3 of water!
If Lipids/fats are present, a cloudy EMULSION is formed
We tend to forget some of these minute details so I though of writing them down !
For almost 10 years, the site XtremePapers has been trying very hard to serve its users.
However, we are now struggling to cover its operational costs due to unforeseen circumstances. If we helped you in any way, kindly contribute and be the part of this effort. No act of kindness, no matter how small, is ever wasted.
Click here to Donate Now