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Chem ques(...again...)

On heating hydrogen peroxide decomposes according to the equation
2H2O2 ----> 2H2O + O2
Hydrogen peroxide is marketed as an aqueous solution of a given 'volume strength'. The common 20-volume solution gives 20dm^3 of oxygen from 1dm^3 of solution. What is the concentration in gdm^-3 of such a solution?

Suggest in terms of the collision theory why 100-volume hydrogen peroxide (giving 100dm^3 of oxygen from 1dm^3 of hydrogen peroxide when it decomposes to water and oxygen) was used rather than the more common 20-volume solution.

Thanks for your help! *hug*
Reply 1
Avatar for oxymoron
oxymoron
7
Mimo
On heating hydrogen peroxide decomposes according to the equation
2H2O2 ----> 2H2O + O2
Hydrogen peroxide is marketed as an aqueous solution of a given 'volume strength'. The common 20-volume solution gives 20dm^3 of oxygen from 1dm^3 of solution. What is the concentration in gdm^-3 of such a solution?

Suggest in terms of the collision theory why 100-volume hydrogen peroxide (giving 100dm^3 of oxygen from 1dm^3 of hydrogen peroxide when it decomposes to water and oxygen) was used rather than the more common 20-volume solution.

Thanks for your help! *hug*


The solution gives 20dm3 of oxygen = 20/24 moles = 0.833 moles

So from equation, the 1dm3 of H2O2 solution must contain 2 x 0.833 = 1.67 moles of H202

So moles of H2O2 in 1dm3 = 1.67
So grams of H2O2 in 1dm3 = 1.67 x rmm
=1.67 x 34
=56.7g

so Concentration = 56.7 g/dm3

Second part: 100-volume solution was used in what? The answer could just be "because it's more concentrated"?
Reply 2
Avatar for Mimo
Mimo
OP
Thanks, oxymoron. Sorry I didn't make myself clear on the last question.

Anyone up for more questions? Here's some anyway (it's good practice I guess):

To obtain aminoethane, ethanol is heated with potassium bromide, KBr, and 50% sulphuric acid. The bromoethane produced is then converted to aminoethane.
1) Suggest why 50% H2SO4 is used rather than concentrated.
2) Give reagents and conditions needed to convert bromoethane to aminoethane.
:smile:
1. to prevent dehydration of the ethanol --> ethene
2) Give reagents and conditions needed to convert bromoethane to aminoethane.

Mix with alcoholic ammonia, and heat under pressure.
Reply 5
Avatar for Mimo
Mimo
OP
Got it! Thanks a bunch to charco and endeavour- you both have helped me out so much, I really appreciate it.

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