A radioactive substance decays exponentially. a scientist begins with 120 milligrams of a radioactive substance. after 14 hours,
1 answer:
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Explanation:
It is known that of
=
.
(a) Relation between and
is as follows.
Putting the values into the above formula as follows.
=
= 3.347
Also, relation between pH and is as follows.
pH =
=
= 3.44
Therefore, pH of the buffer is 3.44.
(b) No. of moles of HCl added =
=
= 0.0116 mol
In the given reaction, will react with
to form
Hence, before the reaction:
No. of moles of =
= 0.15 mol
And, no. of moles of =
= 0.12 mol
On the other hand, after the reaction :
No. of moles of = moles present initially - moles added
= (0.15 - 0.0116) mol
= 0.1384 mol
Moles of = moles present initially + moles added
= (0.12 + 0.0116) mol
= 0.1316 mol
As, =
=
= 3.347
Since, volume is both in numerator and denominator, we can use mol instead of concentration.
As, pH =
= 3.347+ log {0.1384/0.1316}
= 3.369
= 3.37 (approx)
Thus, we can conclude that pH after the addition of 1.00 mL of 11.6 M HCl to 1.00 L of the buffer solution is 3.37.