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# pH Watch

1. of of HCl was mixed with of water. Determine the pH of the diluted acid.

the answer is 2.31 but how do i get to this?
Thanks
2. (Original post by master y)
of of HCl was mixed with of water. Determine the pH of the diluted acid.

the answer is 2.31 but how do i get to this?
Thanks
You can't -log(0.02) because the HCl concentration is more dilute when you add the water.

Because of this you need to do the following
1. c*v=n so 0.02*0.025= 0.0005 moles [this gives you the no. of moles in 25cm3]
2. n/v=c so (0.0005)/0.1= 0.005 [this gives you the 'new' conc. of HCl in 100cm3 ]
3. now simply -log(0.005)= 2.301
3. (Original post by freetown)
You can't -log(0.02) because the HCl concentration is more dilute when you add the water.

Because of this you need to do the following
1. c*v=n so 0.02*0.025= 0.0005 moles [this gives you the no. of moles in 25cm3]
2. n/v=c so (0.0005)/0.1= 0.005 [this gives you the 'new' conc. of HCl in 100cm3 ]
3. now simply -log(0.005)= 2.301

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