Biology; Chemistry; Physics: Post your doubts here!

[CoolBreeze]

PLZ tell the ans of part ii

 

[CoolBreeze]

What do they mean in the f part!!! Plzz explain term by term!!

 

[scouserlfc]

What do they mean in the f part!!! Plzz explain term by term!!View attachment 20444

What it means is that u have to actually know the meaning of those words at the end like thinking distance braking distance etc .....
then u have to actually be able to solve the effects on the friction of a moving vehicle like the effect of increasing thinking distance or breaking distance then what happens also effects which reduce friction like tyre surface whether it can grip well like when its worn out or when the road is slippery etc. so u have to be able to interpret the effects of this on friction thats all !

PLZ tell the ans of part iiView attachment 20443

Well since u increased the force to 20N and the old force was 10N where the object was moving with constant speed therefore the frictional force is 10N so using Newtons Second law :
20-10=2a
a=5 m/s^2

Hello, I'm here with some questions, that will be really helpful if u people can solve it, with explanation .

Q1. In term of structure, explain why the melting point of MgO is higher than that of MgO.

These one with .jpg files
View attachment 20406View attachment 20407 View attachment 20408

Cant do Q 1 because u havent specified correctly what u want to compare MgO with !

Q2 is an A Level question surprised you are doing these when in A Levels (if u still need the answer then tell me )

Q3 is basically the reaction of Nitrogen with Oxygen as u know that N2 is inert in the atmosphere because the reaction with O2 requires lots of heat and is endothermic it takes place during lightning !
therefore V and W are oxygen and Nitrogen respectively they at first form NO then as NO reacts with more V they form NO2 the brown gas ! which then reacts with oxygen and water to form Nitric acid ! the constituent of acid rain !

For the reaction of Al with Hcl use the equation below
2Al + 6HCl ----> 2AlCl3 + 3H2
Now work your way through by using 100cm^3 of H2,find the moles of H2 then use ratio and get Al moles and then find its mass using its Atomic mass !

Q4 again wont advise you to do them but tell me where u got these questions i wonder if u are doing IGCSE ! do tell ?

 

[mustafa ali]

i have to give the chemistry paper in this year...and i have started to study from jan and iam feelings difficulties from where to start the preparetion..does any one have some tricks for my prepareration

 

[Iishrak]

M

What it means is that u have to actually know the meaning of those words at the end like thinking distance braking distance etc .....
then u have to actually be able to solve the effects on the friction of a moving vehicle like the effect of increasing thinking distance or breaking distance then what happens also effects which reduce friction like tyre surface whether it can grip well like when its worn out or when the road is slippery etc. so u have to be able to interpret the effects of this on friction thats all !




Well since u increased the force to 20N and the old force was 10N where the object was moving with constant speed therefore the frictional force is 10N so using Newtons Second law :
20-10=2a
a=5 m/s^2



Cant do Q 1 because u havent specified correctly what u want to compare MgO with !

Q2 is an A Level question surprised you are doing these when in A Levels (if u still need the answer then tell me )

Q3 is basically the reaction of Nitrogen with Oxygen as u know that N2 is inert in the atmosphere because the reaction with O2 requires lots of heat and is endothermic it takes place during lightning !
therefore V and W are oxygen and Nitrogen respectively they at first form NO then as NO reacts with more V they form NO2 the brown gas ! which then reacts with oxygen and water to form Nitric acid ! the constituent of acid rain !

For the reaction of Al with Hcl use the equation below
2Al + 6HCl ----> 2AlCl3 + 3H2
Now work your way through by using 100cm^3 of H2,find the moles of H2 then use ratio and get Al moles and then find its mass using its Atomic mass !

Q4 again wont advise you to do them but tell me where u got these questions i wonder if u are doing IGCSE ! do tell ?

Mgo with Na2O, sorry typing mistake...

and no these came in the mock exam, and the teacher suck she can't really explain it, i'll give CIE o level this year, -_- , and yes i do need that answer , i'll b giving retest tomorrow, cause i failed this time..

 

[Iishrak]

i have to give the chemistry paper in this year...and i have started to study from jan and iam feelings difficulties from where to start the preparetion..does any one have some tricks for my prepareration

After going through each chapter, read the redspot topical questions, You'll then get accustomed to the type of question, and sometimes you can just assume the answer without actually knowing the answer and it will turn right

if there was no redspot, i'd stop studying

 

[scouserlfc]

M
Mgo with Na2O, sorry typing mistake...

and no these came in the mock exam, and the teacher suck she can't really explain it, i'll give CIE o level this year, -_- , and yes i do need that answer , i'll b giving retest tomorrow, cause i failed this time..

For MgO thing !
The charge on MgO is +2 and -2 while that on Na2O is +1 and -1 so that means there is greater attraction between unlike ions in MgO than in Na2O also due to both ions in MgO have a much smaller radius than Na2O there is much more energy required to seperate these ions than Na2O !

For the question of alcohol and K2Cr2O7 i forgot man that was in O Levels too it forms a Carbooxhylic acid actually,whichever the alcohol it is like if it was propanol then it forms propanoic acid ! so here as u have two OH groups u will actually form two -COOH groups !
The ester formed between propanoic acid and ethanol is ethyl propanoate and water too but the main thing is ethyl propanoate ! Just go through this reaction from your book its an important one !
For the formation of alkene from alcohol (this is seriously A level stuff dude you should tell your teacher its not in the CIE syllabus ! ) Anyways u use exact same apparatus as cracking and heat with Al2O3 catalyst which results in forming steam and the alkene the gas are collected by passing the tube coming out of the heating tube into a beaker containing water and the alkene which is insoluble in water moves out of water where u can collect,although u would require to dry it up !

The last attachment question is purely the moles question u should know how to do this,or else u will surely get a poor grade in CIE,start practicing these questions by doing the ATP papers !
a)find moles of CO2 using the formula
Volume = moles * molar volume
b) now see the ratio its 1:1 for CO2 and NaHCO3 thereofre it also has the same moles !
Just find its mass by using the equation mole=(mass/molecular mass )
c) use the formula (actual value)/(experimental or calculated value) * 100

d) its not done because CO2 is slightly soluble and forms carbonic acid in water !
e) water of crystallisation is the water which is essential for the crystal to remain in its crystalline state however it can be removed ! (the formula it asks even i dont know it yet,but it is Na2CO3.10H20

f) Just use this formula for the crystal i stated above !
(molecular mass of water in crystal)/(molecular mass of crystal whole ! ) *100

 

[MuslimGirl]

AOA Wr Wb...

I read this on some website.... i am damn confused.... help me :O

 

[robinhoodmustafa]

AOA Wr Wb...

I read this on some website.... i am damn confused.... help me :O

View attachment 20464

This Is wrong . The Best way to differentiate b/w Exo and Endo is by MEXBEND "Making Exo , Breaking Endo

 

[Suchal Riaz]

AOA Wr Wb...

I read this on some website.... i am damn confused.... help me :O

View attachment 20464

this is wrong. when energy is taken in the beaker or surroundings get colder and in exothermic, you know well if you ever saw something burning(but this is not the only exothermic reaction)

 

[papajohn]

Anyone know how to solve the MCQ relating to Colour code of resistor.

 

[avenger]

AOA Wr Wb...

I read this on some website.... i am damn confused.... help me :O

View attachment 20464

This is wrong. It's the other way round actually.

 

[Mariyam zia]

u'll use F=ma n make a as the subject and take out the force difference 20-10
10/2= 5m/s

 

[Suchal Riaz]

if there was no redspot, i'd stop studying

I can bet on this. you won't stop your study if ur redspot is taken away.

 

[Iishrak]

w

I can bet on this. you won't stop your study if ur redspot is taken away.

well i'd have poor grades, and my interest of studying would be gradually lost to a great extent

 

[Iishrak]

thank

For MgO thing !
The charge on MgO is +2 and -2 while that on Na2O is +1 and -1 so that means there is greater attraction between unlike ions in MgO than in Na2O also due to both ions in MgO have a much smaller radius than Na2O there is much more energy required to seperate these ions than Na2O !

For the question of alcohol and K2Cr2O7 i forgot man that was in O Levels too it forms a Carbooxhylic acid actually,whichever the alcohol it is like if it was propanol then it forms propanoic acid ! so here as u have two OH groups u will actually form two -COOH groups !
The ester formed between propanoic acid and ethanol is ethyl propanoate and water too but the main thing is ethyl propanoate ! Just go through this reaction from your book its an important one !
For the formation of alkene from alcohol (this is seriously A level stuff dude you should tell your teacher its not in the CIE syllabus ! ) Anyways u use exact same apparatus as cracking and heat with Al2O3 catalyst which results in forming steam and the alkene the gas are collected by passing the tube coming out of the heating tube into a beaker containing water and the alkene which is insoluble in water moves out of water where u can collect,although u would require to dry it up !

The last attachment question is purely the moles question u should know how to do this,or else u will surely get a poor grade in CIE,start practicing these questions by doing the ATP papers !
a)find moles of CO2 using the formula
Volume = moles * molar volume
b) now see the ratio its 1:1 for CO2 and NaHCO3 thereofre it also has the same moles !
Just find its mass by using the equation mole=(mass/molecular mass )
c) use the formula (actual value)/(experimental or calculated value) * 100

d) its not done because CO2 is slightly soluble and forms carbonic acid in water !
e) water of crystallisation is the water which is essential for the crystal to remain in its crystalline state however it can be removed ! (the formula it asks even i dont know it yet,but it is Na2CO3.10H20

f) Just use this formula for the crystal i stated above !
(molecular mass of water in crystal)/(molecular mass of crystal whole ! ) *100

thanks , moles is the hardest chapter to me after organic chemistry :S

 

[scouserlfc]

thank
thanks , moles is the hardest chapter to me after organic chemistry :S

Nothing is hard,its you who make it hard just think positively about it and do the thing dont make up your mind before hand that organic is difficult it may be the general opinion but it certainly is not

 

[Suchal Riaz]

thank
thanks , moles is the hardest chapter to me after organic chemistry :S

do few questions everyday of moles and organic. just as much questions that you are comfortable with them. inshallah they will get easier for you.

 

[Mariyam zia]

hey i didnt get the answer of the indentification of X and Y plzzzzzzz help?

 

[Iishrak]

Nothing is hard,its you who make it hard just think positively about it and do the thing dont make up your mind before hand that organic is difficult it may be the general opinion but it certainly is not

easy for you to say :/, anyway i passed in the retest