What is the ph of a 100 ml solution containing 0.0040 g of HCl?
Answers
The first thing to do here is to calculate the number of moles of hydrochloric acid present in that sample. To do that, use the compound's molar mass
0.0040
g
⋅
1 mole HCl
36.46
g
=
0.0001097 moles HCl
Now, hydrochloric acid is a strong acid, which means that it dissociates completely in aqueous solution to produce hydronium cations,
H
3
O
+
HCl
(
a
q
)
+
H
2
O
(
l
)
→
H
3
O
+
(
a
q
)
+
Cl
−
(
a
q
)
This basically means that every mole of hydrochloric acid dissolved in water will produce
1
mole of hydronium cations.
no. of moles of H
3
O
+
=
0.0001097 moles
The molarity of the hydronium cations must be calculated for
1 L
of solution, so do
1
L solution
⋅
10
3
mL
1
L
⋅
0.0001097 moles H
3
O
+
100
mL solution
=
0.001097 moles H
3
O
+
Since that is how many moles of hydronium cations you have in
1 L
of solution, you can say that the concentration of the hydronium cations will be
[
H
3
O
+
]
=
0.001097 M
The pH of the solution is calculated by taking the negative log of the concentration of hydronium cations
pH
=
−
log
(
[
H
3
O
+
]
)
−−−−−−−−−−−−−−−−−−−−
Plug in your value to find
pH
=
−
log
(
0.001097
)
=
3.0
−−−
The answer is rounded to one decimal place, the number of sig figs you have for the volume of the solution.
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Answer:
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Explanation:
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