Moles Problem!

[Saladin]

Hey, I really dont get this. The question is here.

This is how I did it:

(c)(i)



(ii)

As the ratio of I₂ and CH₃CH₂I is 1:1.

Therefore, it should be something like this:



But this is not the answer. I really not understand how this all works!

[nid404]

2P + 3I2 ? 2PI3
3CH3CH2OH + PI3 ? 3CH3CH2I + H3PO3

Look carefully at the ratio

1:1?

1:2  

[Saladin]

2P + 3I2 ? 2PI3
3CH3CH2OH + PI3 ? 3CH3CH2I + H3PO3

Look carefully at the ratio

1:1?

1:2  

Thats what I dont get, how is it 1:2?

[Meticulous]

Exactly..look carefully at the ratios

2PI₃ ----> I₂

PI₃ ---> 3CH_3CH2I

first find the moles of PI₃ : 0.0788* 2/3 =0.05253

now find iodoethane mole: 3* 0.05253= 0.1576

therefore, mass= 0.1576* 156= 24.6 g

[princess12]

that is the thing i donot get it also how the ratio come always

[tmisterr]

look at the first equation, 3 moles of Iodine form 2 moles of PI₃ so 0.079 will form (0.079*2/3) moles of PI₃. And now the second equation, one mole of PI₃ will form 3 moles of Iodoethane so ((0.079*2/3)*3)=0.158 moles of iodoethane which is equal to 24.648 grams

[nid404]

Basically

3moles of I2 gives 2 moles of PI3

the next reaction uses only one mole of PI3   ---> multiplying this eqn by 2 will give you the ratio


 
Hope ur gettin me