Chemistry Question please heeeelppppp?
2020-08-19 4:37 pm
Phosphorus forms two compounds with chlorine. In the first, 1,000g of phosphorus was combined with 3,433g of chlorine, and in the second, 2,500g of phosphorus was combined with 14,308g of chlorine. Show that these results obey the dalton multiple law of proportions.
回答 (3)
2020-08-19 4:50 pm
✔ 最佳答案
When reacting with 1 g of P,(Mass of Cl in the 1st compound) : (Mass of Cl in the 2nd compound)
= (3,433/1,000) : (14,308/2,500)
= 3.433 : 5.723
= (3.433/3.433) : (5.723/3.433)
= 1 : 1.667
= (1 × 3) : (1.667 × 3)
= 3 : 5
3 : 5 is a simple ratio. Hence, the results obey the Dalton's multiple law of proportions.
2020-08-20 4:46 am
You can read the definition of the law of multiple proportions here
https://en.wikipedia.org/wiki/Law_of_multiple_proportions
and see a couple of examples.
BUT.. the easy way to demonstrate this is by interpreting the law like this
.. "the ratios of the ratios of the masses of elements 1 to element 2
.. .in the compounds is a ratio of small whole numbers"
ie.
.. . (1000 / 3433)
.. ----- ---- ----- ---- = 1.67 = 5 / 3
.. . (2500 / 14308)
5 and 3 are small whole numbers
problem solved!
*********
*********
and this makes sense because if we do the math, we see our compounds are
compound #1
.. moles P = 1000g * (1mol / 30.97g) = 32.2
.. moles Cl = 3433g * (1mol / 35.45g) = 96.8
.. compound is PCl3
compound #2
.. moles P = 2500g * (1mol / 30.97g) = 80.7
.. moles Cl = 14308g * (1mol / 35.45g) = 403.7
.. compound is PCl5
and
.. we can see where the 3 and 5 come from
the idea with Daltons law is that when 2 elements form a series of compounds, the mass of the compounds changes as we add (or subtract) integer number of atoms.
**********
excellent work MicatKie
David.. you ridicule Micatkie for making the process complicated, but you're doing the same math + adding an extra step to make the mass of P constant. You don't need to do that..That's not what the law of multiple proportions is all about.
https://en.wikipedia.org/wiki/Law_of_multiple_proportions
and see a couple of examples.
BUT.. the easy way to demonstrate this is by interpreting the law like this
.. "the ratios of the ratios of the masses of elements 1 to element 2
.. .in the compounds is a ratio of small whole numbers"
ie.
.. . (1000 / 3433)
.. ----- ---- ----- ---- = 1.67 = 5 / 3
.. . (2500 / 14308)
5 and 3 are small whole numbers
problem solved!
*********
*********
and this makes sense because if we do the math, we see our compounds are
compound #1
.. moles P = 1000g * (1mol / 30.97g) = 32.2
.. moles Cl = 3433g * (1mol / 35.45g) = 96.8
.. compound is PCl3
compound #2
.. moles P = 2500g * (1mol / 30.97g) = 80.7
.. moles Cl = 14308g * (1mol / 35.45g) = 403.7
.. compound is PCl5
and
.. we can see where the 3 and 5 come from
the idea with Daltons law is that when 2 elements form a series of compounds, the mass of the compounds changes as we add (or subtract) integer number of atoms.
**********
excellent work MicatKie
David.. you ridicule Micatkie for making the process complicated, but you're doing the same math + adding an extra step to make the mass of P constant. You don't need to do that..That's not what the law of multiple proportions is all about.
2020-08-19 8:30 pm
micatkie's solution might be right ... but it seems too complicated
The law of mutiple prop. states that one of the elements must be constant mass .. these are not
1st ... P:Cl = 1g to 3.433
2nd ... P:Cl = 2.5 to 14.308
multiply the 1st by 2.5
(1 X 2.5) to (3.433 X 2.5) = 2.5 to 8.5825
.... now the mass of P is constant .. what is the ratio of Cl
8.5825/ 14.308 = 0.59984 rounds to 0.6 .. or 6/10
... reduces to 3/5 <<< small whole number ratio of Cl
so this confirmes the law of mult. proportions
The law of mutiple prop. states that one of the elements must be constant mass .. these are not
1st ... P:Cl = 1g to 3.433
2nd ... P:Cl = 2.5 to 14.308
multiply the 1st by 2.5
(1 X 2.5) to (3.433 X 2.5) = 2.5 to 8.5825
.... now the mass of P is constant .. what is the ratio of Cl
8.5825/ 14.308 = 0.59984 rounds to 0.6 .. or 6/10
... reduces to 3/5 <<< small whole number ratio of Cl
so this confirmes the law of mult. proportions
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