(a)
pH = 4.77
; (b)
[
H
3
O
+
]
=
1.00
×
10
-4
l
mol/dm
3
; (c)
[
A
-
]
=
0.16 mol⋅dm
-3
Explanation:
(a) pH of aspirin solution
Let's write the chemical equation as
m
m
m
m
m
m
m
m
l
HA
m
+
m
H
2
O
⇌
H
3
O
+
m
+
m
l
A
-
I/mol⋅dm
-3
:
m
m
0.05
m
m
m
m
m
m
m
m
l
0
m
m
m
m
m
l
l
0
C/mol⋅dm
-3
:
m
m
l
-
x
m
m
m
m
m
m
m
m
+
x
m
l
m
m
m
l
+
x
E/mol⋅dm
-3
:
m
0.05 -
l
x
m
m
m
m
m
m
m
l
x
m
m
x
m
m
m
x
K
a
=
[
H
3
O
+
]
[
A
-
]
[
HA
]
=
x
2
0.05 -
l
x
=
3.27
×
10
-4
Check for negligibility
0.05
3.27
×
10
-4
=
153
<
400
∴
x
is not less than 5 % of the initial concentration of
[
HA
]
.
We cannot ignore it in comparison with 0.05, so we must solve a quadratic.
Then
x
2
0.05
−
x
=
3.27
×
10
-4
x
2
=
3.27
×
10
-4
(
0.05
−
x
)
=
1.635
×
10
-5
−
3.27
×
10
-4
x
x
2
+
3.27
×
10
-4
x
−
1.635
×
10
-5
=
0
x
=
1.68
×
10
-5
[
H
3
O
+
]
=
x
l
mol/L
=
1.68
×
10
-5
l
mol/L
pH
=
-log
[
H
3
O
+
]
=
-log
(
1.68
×
10
-5
)
=
4.77
(b)
[
H
3
O
+
]
at pH 4
[
H
3
O
+
]
=
10
-pH
l
mol/L
=
1.00
×
10
-4
l
mol/L
(c) Concentration of
A
-
in the buffer
We can now use the Henderson-Hasselbalch equation to calculate the
[
A
-
]
.
pH
=
p
K
a
+
log
(
[
A
-
]
[
HA
]
)
4.00
=
−
log
(
3.27
×
10
-4
)
+
log
(
[
A
-
]
0.05
)
=
3.49
+
log
(
[
A
-
]
0.05
)
log
(
[
A
-
]
0.05
)
=
4.00 - 3.49
=
0.51
[
A
-
]
0.05
=
10
0.51
=
3.24
[
A
-
]
=
0.05
×
3.24
=
0.16
The concentration of
A
-
in the buffer is 0.16 mol/L.
hope this helps :)
FeSO₄*7H₂O(s) = FeSO₄(s) + 7H₂O(g)
M(FeSO₄*7H₂O)=278.0 g/mol
M(FeSO₄)=151.9 g/mol
m(FeSO₄*7H₂O)/M(FeSO₄*7H₂O)=m(FeSO₄)/M(FeSO₄)
m(FeSO₄)=M(FeSO₄)m(FeSO₄*7H₂O)/M(FeSO₄*7H₂O)
m(FeSO₄)=151.9*100.0/278.0=54.6 g
m(FeSO₄)=54.6 g
Answer:
Syrup is a mixture of thick sticky liquid consisting of a concentrated solution of sugar and water with or without the addition of a flavoring agent or medicinal substance.
Explanation:
so compound
Answer:
1.02mole
Explanation:
The reaction equation is given as:
2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
Given:
Mass of H₂SO₄ = 50g
Unknown:
Number of moles of NaOH = ?
Solution:
To solve this problem, we first find the number of moles of the acid given;
Number of moles = 
Molar mass of H₂SO₄ = 2(1) + 32 + 4(16) = 98g/mol
Now;
Number of moles = 
= 0.51mole
From the balanced reaction equation:
1 mole of H₂SO₄ will be neutralized by 2 mole of NaOH
0.51 mole of H₂SO₄ will be neutralized by 2 x 0.51 = 1.02mole of NaOH
Explanation:
In order to go from mass of magnesium to atoms of magnesium, we have to do two things:
Convert mass of Mg to moles of Mg using the molar mass of Mg as a conversion factor
Convert moles of Mg to atoms of Mg using Avogadro's number (6.02×1023) as a conversion factor
Step 1:
Before we start, I should note that the molar mass of Mg is 24.31gmol. We can go from mass to moles using dimensional analysis. The key to dimensional analysis is understanding that the units that you don't need any more cancel out, leaving the units that are desired:
48.60g
×1mol24.31g
=2.00mol
Step 2:
We'll use this relationship:
www.sprinklernewz.uswww.sprinklernewz.us
Using the moles of Mg that we just obtained, we can use Avogrado's number to perform dimensional analysis in order to cancel out units of mol to end up with atoms of Mg:
2.00mol
×6.02×1023atoms1mol
=1.204×1024atoms
Thus, 48.60g of Mg is equivalent to 1.204×1024atoms
Hope this helped :)
