Answer:
7.41 × 10⁻⁵
Explanation:
Let's consider the basic dissociation reaction of trimethylamine (CH₃)N).
(CH₃)N + H₂O = (CH₃)NH⁺ + OH⁻
According to Brönsted-Lowry, in this reaction (CH₃)N is a base and (CH₃)NH⁺ is its conjugate acid. The pKb for (CH₃)N is 9.87. We can calculate the pKa of (CH₃)NH⁺ using the following expression.
pKa + pKb = 14
pKa = 14 - pKb = 14 - 9.87 = 4.13
Then, we can calculate the acid dissociation constant for (CH₃)NH⁺ using the following expression.
pKa = -log Ka
Ka = antilog - pKa = antilog -4.13 = 7.41 × 10⁻⁵
Remember that in this case pressure is equal to 1.00 atm and temperature is equal to 273.15K. So,
P
V
=
n
R
T
→
n
=
P
V
R
T
=
1.00
a
t
m
⋅
7.0
L
0.082
a
t
m
⋅
L
m
o
l
⋅
K
⋅
273.15
K
=
0.31
Since we know hydrogen's molar mass (
2.0
g
m
o
l
), we can determine the mass
m
H
2
=
n
⋅
m
o
l
a
r
.
m
a
s
s
=
0.31
m
o
l
e
s
⋅
2.0
g
m
o
l
=
0.62
g
If indeed you are dealing with STP, remember that, under these conditions, 1 mole of any ideal gas occupies
22.4
L
. So,
n
=
V
V
m
o
l
a
r
=
7.0
L
22.4
L
=
0.31
moles
And, once again,
m
=
0.31
⋅
2.0
=
0.6
Do you know what mixture it is talking about?
Use the grams to moles first. The molar mass of sodium is 22.99g, so 10/22.99 ≈ 0.43 moles. The use moles to atoms conversions. 0.43 x (6.022 x 10^23), which would be about 2.62 x 10^23 atoms in 10g of sodium.
All of the group iia metals (the column with Be, Mg, Ca, etc) have an outermost s suborbital with 2 electrons
