Chemistry paper 5 M/J 2018

[sterryfox]

write down any answers you remember from the paper you just took so people can compare them

 

[anastasia grey113]

This discussion is going on in the thread Chemistry: Post your doubts here

 

[Anas Patel]

For why to use digital probe thermometer instead of lab thermometer, I wrote because it has less % error since lab thermometer is 1 dp and digital is 2 dp.
For why the B.P is not 100C but 99.48C, I wrote heat is lost to surroundings.
For the 2nd Q, 1st part, I wrote the more no. Of moles means Delta Twill increase. Since DeltaT is difference between temp of water, which is constant, and temp of solution, the temp of solution increases. So temperature increases as pressure decreases.
For 1st question 1 st part, I wrote Precaution as wear gloves.
For 2nd part, no change at positive electrode and red at negative.
The salt I chose in the experiment 1 and experiment 2 question (Last question of that page I guess, 2 marks) was KCl.
Mass of K2SO4 was around 1.743 g???
Volume needed to dilute was 5 cm3???
For the preparation of solution from mass Of K2SO4, I wrote: Add 1.743 g of K2SO4 To a beaker. Add 50cm3 of water using a burette. Transfer the contents to a volumetric flask. Rinse the beaker. Stopper the flask and shake thoroughly. Add 50 cm3 of water again using a burette to the volumetric flask. Stopper the flask and shake thouroughly.
For the apparatus needed to measure that 5cm3 , I wrote a graduated pipette.
For the question on Expermient1 and experiment 2, which was what happens when you increase the charge from -1 to -2 to -3, I wrote: As the charge becomes more negative, the amount of salt needed to precipitate 1dm3 sol decreases. This is because the concentration of ions increases.

 

[Koolboy1]

For why to use digital probe thermometer instead of lab thermometer, I wrote because it has less % error since lab thermometer is 1 dp and digital is 2 dp.
For why the B.P is not 100C but 99.48C, I wrote heat is lost to surroundings.
For the 2nd Q, 1st part, I wrote the more no. Of moles means Delta Twill increase. Since DeltaT is difference between temp of water, which is constant, and temp of solution, the temp of solution increases. So temperature increases as pressure decreases.
For 1st question 1 st part, I wrote Precaution as wear gloves.
For 2nd part, no change at positive electrode and red at negative.
The salt I chose in the experiment 1 and experiment 2 question (Last question of that page I guess, 2 marks) was KCl.
Mass of K2SO4 was around 1.743 g???
Volume needed to dilute was 5 cm3???
For the preparation of solution from mass Of K2SO4, I wrote: Add 1.743 g of K2SO4 To a beaker. Add 50cm3 of water using a burette. Transfer the contents to a volumetric flask. Rinse the beaker. Stopper the flask and shake thoroughly. Add 50 cm3 of water again using a burette to the volumetric flask. Stopper the flask and shake thouroughly.
For the apparatus needed to measure that 5cm3 , I wrote a graduated pipette.
For the question on Expermient1 and experiment 2, which was what happens when you increase the charge from -1 to -2 to -3, I wrote: As the charge becomes more negative, the amount of salt needed to precipitate 1dm3 sol decreases. This is because the concentration of ions increases.

Which variant did you write?

 

[Heba Nazir]

Which variant did you write?

this is for varient 52

 

[Anas Patel]

Which variant did you write?

52

 

[Tauqir_hamed]

Guys what did you write about what will happen to the temperature of water when sucrose is used instead of glucose, I am talking about varient 52 , question no 2

 

[Dukula Jayasinghe]

Hello.

 

[James Vakil]

For why to use digital probe thermometer instead of lab thermometer, I wrote because it has less % error since lab thermometer is 1 dp and digital is 2 dp.
For why the B.P is not 100C but 99.48C, I wrote heat is lost to surroundings.
For the 2nd Q, 1st part, I wrote the more no. Of moles means Delta Twill increase. Since DeltaT is difference between temp of water, which is constant, and temp of solution, the temp of solution increases. So temperature increases as pressure decreases.
For 1st question 1 st part, I wrote Precaution as wear gloves.
For 2nd part, no change at positive electrode and red at negative.
The salt I chose in the experiment 1 and experiment 2 question (Last question of that page I guess, 2 marks) was KCl.
Mass of K2SO4 was around 1.743 g???
Volume needed to dilute was 5 cm3???
For the preparation of solution from mass Of K2SO4, I wrote: Add 1.743 g of K2SO4 To a beaker. Add 50cm3 of water using a burette. Transfer the contents to a volumetric flask. Rinse the beaker. Stopper the flask and shake thoroughly. Add 50 cm3 of water again using a burette to the volumetric flask. Stopper the flask and shake thouroughly.
For the apparatus needed to measure that 5cm3 , I wrote a graduated pipette.
For the question on Expermient1 and experiment 2, which was what happens when you increase the charge from -1 to -2 to -3, I wrote: As the charge becomes more negative, the amount of salt needed to precipitate 1dm3 sol decreases. This is because the concentration of ions increases.

1. Digital probe - That could be an answer but I think it has more to do with the fact that laboratory thermometer can't provide an acceptable level of accuracy (nearest 0.5 or 0.1 degree Celsius) whereas the digital probe is to the closest 0.01 degree celsius.
2. Why B.P. isn't 100 it can't be heat lost to surroundings since it was boiling - boiling happens at constant temp and the question suggested the constant temp was 99.48 degree celsius. I think the answer is that the room was not at 1atp and was in fact less than that (because of the geographic location - altitude?)
3. Change in color is probably colorless/light red at the positive electrode side and red on the other since sol would move away from the positive electrode.
4. Salt would be AlCl3 i think (not sure) since the most positive Al(3+) would remove the most arsenic. A similar trend to the previous observation.

Everything else seems fine. What about those sucrose/NaCl questions? Sucrose has half the number of molecules in the same mass and NaCl dissociates to give 2 ions whereas glucose only gives 1 so NaCl has twice the boiling constant?

 

[Tauqir_hamed]

FOR THE SUCROSE / GLUCOSE ONE, IS INCREASE IN BOILING POINT ELEVATION CORRECT ? COZ IT SAID SUCROSE IS VERY SOLUBLE IN WATER THAN GLUCOSE ( AND THATS WHAT GOOGLE SAYS AS WELL ) .. SO THE NUMBER OF PARTICLES DISSOLVED INCREASES, AND THE THING THAT THEY HAD ASKED FOR ( i forgot ) ALSO SHOULD INCREASE

 

[Canaday]

52

do you also do physics?