Edexcel CHEMISTRY DOUBTS!!!!

[The Golden Girl =D]

D here are the ppm Questions I told you about .

1. a solution is prepared by dissloving 0.475g of (NH4)2SO4 (Mr =118)in enough of distilled water and the solution is made up to 2.0 dm3

Calculate the ppm of

a] NH4 +                b] SO4  2-

 BOLD is the charge

2. a 10% (by mass) of CO is ...

A. 100,000 ppm
B.  10,000 ppm
C.  28,000 ppm
D. 10,000,000 ppm

3. Fuel manufacturers recommend carbon monoxide levels be between 0.5 to 0.7 % at full load .Many measure CO in parts per million , ppm .
What is concentration in ppm of 0.5 % ?


Thanks In Advance

[Deadly_king]

D here are the ppm Questions I told you about .

2. a 10% (by mass) of CO is ...

A. 100,000 ppm
B.  10,000 ppm
C.  28,000 ppm
D. 10,000,000 ppm

Definition of ppm
This is a way of expressing very dilute concentrations of substances. Just as per cent means out of a hundred, so parts per million or ppm means out of a million. Usually describes the concentration of something in water or soil. One ppm is equivalent to 1 milligram of something per liter of water (mg/l) or 1 milligram of something per kilogram soil (mg/kg).

This somehow eases the 2nd question.

In other words 10/100 of CO is also equal to 100000/1000000 CO.

Hence answer is A.

3. Fuel manufacturers recommend carbon monoxide levels be between 0.5 to 0.7 % at full load .Many measure CO in parts per million , ppm .
What is concentration in ppm of 0.5 % ?

Again since the level of CO is 0.5% : 0.5/100, we just need to convert the denominator from 100 to 1000000.

In this way we'll be getting 5000/1000000.

Hence answer is 5,000 ppm.

If you wanna know more about ppm. click here.

[elemis]

(NH₄)₂SO₄ -----> 2NH₄⁺ + SO₄^2-

0.475/132 = 3.598 *10^-3 moles of Ammonium Sulphate

2*[3.598 *10^-3] = 7.197*10^-3 NH₄⁺ ions

Since concentration = no. of moles / volume

c = 7.197*10^-3 / 2 = 3.598*10^-3 moldm^-3

Converting moldm^-3 to gdm^-3 gives : 0.475 gdm-3

Converting gdm-3 to milligrams per dm3

we get 475 mgdm-3 or 475 ppm

Is this correct ?


It is important to note that 1 ppm = 1 milligram per decimeter cube.

[The Golden Girl =D]

Definition of ppm
This is a way of expressing very dilute concentrations of substances. Just as per cent means out of a hundred, so parts per million or ppm means out of a million. Usually describes the concentration of something in water or soil. One ppm is equivalent to 1 milligram of something per liter of water (mg/l) or 1 milligram of something per kilogram soil (mg/kg).

This somehow eases the 2nd question.

In other words 10/100 of CO is also equal to 100000/1000000 CO.

Hence answer is A.

Again since the level of CO is 0.5% : 0.5/100, we just need to convert the denominator from 100 to 1000000.

In this way we'll be getting 5000/1000000.

Hence answer is 5,000 ppm.

If you wanna know more about ppm. click here.

OMG I didn't know it's that easy 

How about the first Q ?


Sorry I know I got Loads of doubts in other stuff I'll post it as soon as I'm done with it iA

I don't get the dative bond , especially when there is a Q that says which of the compounds has a dative bond , how do I know that ?

I got a problem with naming organic compounds and sometimes the geometric isomers if it's drawn and I'm supposed to name it , you know  (can u give me  a website so that I can have more practice on it ? *

Thanks Loads mates

[elemis]

I've answered the (a) part of the first question. Tell me if my answer is correct.

[The Golden Girl =D]

I've answered the (a) part of the first question. Tell me if my answer is correct.

the thing is the booklet the teacher gave me has NO marking scheme or anything so I don't know 

[elemis]

I don't get the dative bond , especially when there is a Q that says which of the compounds has a dative bond , how do I know that ?

Give me an example question.

[The Golden Girl =D]

Give me an example question.

Which of the following pairs do NOT form a dative covalent bond to each other ?

A. NH3 and H+
B. H2O and H+
C.NH3 and BF3
D.CH4 and AlCl3

the Answer is D

[elemis]

A and B are eliminated because they are textbook examples of dative bonding.

Ammonia and a Hydrogen ion form an Ammonium ion NH4⁺ with a dative bond between Hydrogen ion and Nitrogen.

See pic 1


H2O and H+ form an Oxonium Ion which is again a textbook example of dative bonding.

For C look at pic 2


As we have eliminated A, B and C. D is the only option remaining and hence the answer.

[The Golden Girl =D]

A and B are eliminated because they are textbook examples of dative bonding.

Ammonia and a Hydrogen ion form an Ammonium ion NH4⁺ with a dative bond between Hydrogen ion and Nitrogen.

See pic 1


H2O and H+ form an Oxonium Ion which is again a textbook example of dative bonding.

For C look at pic 2


As we have eliminated A, B and C. D is the only option remaining and hence the answer.

Can u draw D as well so that I can see the difference Please ?

[elemis]

Can u draw D as well so that I can see the difference Please ?

I'm not sure how it will look. I dont even think they bond :S

[Deadly_king]

Which of the following pairs do NOT form a dative covalent bond to each other ?

A. NH3 and H+
B. H2O and H+
C.NH3 and BF3
D.CH4 and AlCl3

the Answer is D

I just wanted to make it clearer.

A dative bond is formed when one of the atoms or molecules forming the final product has a lone pair of electron which it can donate to the other atom or molecule who on the contrary can accept a pair of electron to attain the stable electronic configuration of a stable gas.

A : H⁺ lacks an electron which means its electronic configuration is 1s0. Hence it can accept a pair of electron. This pair of electron comes from the ammonia molecule which has one lone pair of electron on the nitrogen atom which is also bonded to 3 other hydrogen atoms.

D : CH₄ ----> All the atoms involved in this molecule namely both carbon and hydrogen have stable electronic configuration. Hence they cannot form any further bond. All the orbitals of carbon has been filled from the electrons which it is sharing with the 4 hydrogen atoms.

[Deadly_king]

I'm not sure how it will look. I dont even think they bond :S

Indeed they will not form any bond.

They will remain as such; two separate molecules.

This is why it is the answer to the question.

[The Golden Girl =D]

Aha Okay ,now I get it =D

but what abt the naming doubt ?

D can u check the first Q I posted at the ppm ?

thx

[Deadly_king]

Aha Okay ,now I get it =D

but what abt the naming doubt ?

D can u check the first Q I posted at the ppm ?

thx

Am still looking for a website which might help you.

Yeah..............I already did. According to me Ari did it well.

But if you don't understand, do let me know and i'll try to elaborate as much as possible.