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Chemistry: Post your doubts here!

Mstudent

Mstudent

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anastasia grey113 said:
Well you see in the 2nd question, the temperature is found by extending another line across the first three points after the sample was added
While in the first one, the already extrapolated line is used rather than extending another line through the first and second point after the sample was added
The question is that in the first question why is the line with the negative gradient (one showing falling temperature) considered to find the temperature rise unlike in the 2nd question in which the line with the positive gradient (one showing rising temperature) used?
Click to expand...

The positive grad aint being used in the second question, the negative grad is, just like in first question. That's how you're supposed to do it. you can never draw a line of best fit with just a few points, only possible with more than 5 pts on graph, so the line with negative grad. in both the cases
 
anastasia grey113

anastasia grey113

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Mstudent said:
The positive grad aint being used in the second question, the negative grad is, just like in first question. That's how you're supposed to do it. you can never draw a line of best fit with just a few points, only possible with more than 5 pts on graph, so the line with negative grad. in both the cases
Click to expand...
well idk my teacher checked it and he didn't award me a mark for it :/
and theres nothing in the marking scheme which helps :/
u sure its supposed to be done that way?
 
Fareez

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Problem 1: A saturated aqueous solution of magnesium methanoate, Mg(HCOO)2, has a solubility of approximately 150 g dm-3 at room temperature. Its exact solubility can be determined by titrating magnesium methanote against aqueous potassium manganate (VII).

During the titration, the methanoate ion, HCOO-, is oxidizes to carbon dioxide while the manganate (VII) ion, MnO4-, is reduced to Mn2+.

You are supplied with

A saturated aqueous solution of Mg(HCOO)2

Aqueous potassium manganate (VII), KMnO4, of concentration 0.0200 mol dm-3

(a) (i). write the half equations for the oxidation of HCOO-(aq) to CO2(g) and the reduction of MnO4-(aq) to Mn2+ (aq) in acid solution.

(ii) Using the approximately solubility above, calculate the concentration, in mol dm-3, of the saturated aqueous magnesium methanoate and the concentration of the methanoate ions present in this solution

(Ai: H, 1.0, C, 12.0, O, 16.0, Mg, 24.3)

(iii) In order to obtain a reliable titre value, the saturated solution of magnesium methanoate needs to be diluted.

Describe how you would accurately measure a 5.0cm3 sample of saturated magnesium methanate solution and use it to prepare a solution fifty times more dilute than the saturated solution.

(vi) 1 mol of acidified MnO4- ions reacts with 2.5 mol of HCOO- ions.

25.0 cm3 of the diluted solution prepared in (iii) required 25.5 cm3 of 0.0200 mol dm-3 potassium manganate (VII) solution to reach the end point.

Use this information to calculate the concentration, in mol dm-3, of HCOO- ions in the diluted solution.

(Vii) use your answer to calculate the concentration of the saturated solution of magnesium methanoate


Can someone help me with vii
 
anastasia grey113

anastasia grey113

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Fareez said:
Problem 1: A saturated aqueous solution of magnesium methanoate, Mg(HCOO)2, has a solubility of approximately 150 g dm-3 at room temperature. Its exact solubility can be determined by titrating magnesium methanote against aqueous potassium manganate (VII).

During the titration, the methanoate ion, HCOO-, is oxidizes to carbon dioxide while the manganate (VII) ion, MnO4-, is reduced to Mn2+.

You are supplied with

A saturated aqueous solution of Mg(HCOO)2

Aqueous potassium manganate (VII), KMnO4, of concentration 0.0200 mol dm-3

(a) (i). write the half equations for the oxidation of HCOO-(aq) to CO2(g) and the reduction of MnO4-(aq) to Mn2+ (aq) in acid solution.

(ii) Using the approximately solubility above, calculate the concentration, in mol dm-3, of the saturated aqueous magnesium methanoate and the concentration of the methanoate ions present in this solution

(Ai: H, 1.0, C, 12.0, O, 16.0, Mg, 24.3)

(iii) In order to obtain a reliable titre value, the saturated solution of magnesium methanoate needs to be diluted.

Describe how you would accurately measure a 5.0cm3 sample of saturated magnesium methanate solution and use it to prepare a solution fifty times more dilute than the saturated solution.

(vi) 1 mol of acidified MnO4- ions reacts with 2.5 mol of HCOO- ions.

25.0 cm3 of the diluted solution prepared in (iii) required 25.5 cm3 of 0.0200 mol dm-3 potassium manganate (VII) solution to reach the end point.

Use this information to calculate the concentration, in mol dm-3, of HCOO- ions in the diluted solution.

(Vii) use your answer to calculate the concentration of the saturated solution of magnesium methanoate


Can someone help me with vii
Click to expand...
View the quoted post below.
anastasia grey113 said:
Because they are asking for concentration of SATURATED solution
And the concentration calculated in previous part is of dilute solution
and saturated solution is 50 times saturated so 50 times r the moles of Mg(HCOO-)2
but u see there r 2 moles of HCOO- in 1 mole of Mg(HCOO-)2
so just multiply it by 50/2 = 25
Click to expand...
 
ErosKuikel

ErosKuikel

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I have no idea how to approach this question . I dont even know what is happening . Anyone, please care to explain this in detail.....
 

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bassamkhan35

bassamkhan35

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Hey everyone out there. I was wondering if someone has the same paper variant as me in other countries so that due to time difference we can help with the questions coming. My paper variants are listed below.
Physics 22, physics 12 physics 33
Chemistry 22, Chemistry 12 and Chemistry 33
Mathematics 12 and Mathematics 62
My time zone Pakistan Standard time GMT+5
 
Mstudent

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Could anyone give me any tips on how to answer questions about anomalous points and explaining why they are anomalous? PLZ help me out

I really can't give any reasons to why they are anomalous
 
anastasia grey113

anastasia grey113

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Mstudent said:
ANd can anyone explain what we draw when they want construction lines in finding grad from graph??
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well basically a triangle joining the two points v take to measure gradient with the best fit line as the hypotenuse.
Mstudent said:
Could anyone give me any tips on how to answer questions about anomalous points and explaining why they are anomalous? PLZ help me out

I really can't give any reasons to why they are anomalous
Click to expand...
well that will come by practice
there is no specific formula or concept to determine them cuz u know any kind of question can come up
u just have to think critically
but let me tell u...where time is involved whether on the x axis or as a constant, it is usually considered to be the cause of anomaly i.e. the reading might have been taken too early or too late.
but then again, there r exceptions :/
 
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