Hey there!
27 tells us the sum of protons and neutrons is 27.
Al tells us we have 13 protons.
3- tells us that there are 3 more electrons than protons.
13 + n = 27
neutrons = 14
13 + 3 = 16 electrons
27Al3- has 13 protons, 14 neutrons, and 16 electrons.
Hope this helps!
Answer: I remember looking out of the car as we pulled up to the Frantz school.”
“I thought maybe it was Mardi Gras.”
“As we walked through the crowd, I didn’t see any faces.”
“[The school] looked bigger and nicer than my old school.”
“The crowd behind us made me think this was an important place.”
“It must be college, I thought to myself.
Explanation:
Answer:
As you go down group 1, the number of electron shells increases – lithium has two, sodium has three, and so forth. The attraction from the positive nucleus to the negative electron is less. This makes it easier to remove the electron and makes the atom more reactive.
If the Ka of HCN = 5.0 x 10^-10
Since
(Ka) (Ka) - 1 x 10^ -14
then
the Kb of its conjugate base (CN-) = 2.0 X 10^-5
since
pH + pOH = 14
when the pH = 10.00
then
the pOH = 4.00
& the OH-
would then equal 1.0 X 10^-4
NaCN as a base does a hydrolysis in water:
CN- & water --> HCN & OH-
notice that equal amounts of OH- & HCN are formed
Kb = [HCN] [OH-] / [CN-]
2.0 X 10^-5 = [1.0 X 10^-4] [1.0 X 10^-4] / [CN-]
[CN-] =(1.0 X 10^-8) / (2.0 X 10^-5)
[CN-] = (5.0 X 10^-4)
that's 0.00050 Molar
which is 0.00050 moles in each liter of aqueous KCN solution
which is
0.00025 moles KCN in 500. mL of aqueous KCN solution
use molar mass of KCN, to find grams:
(0.00025 moles KCN) (65.12 grams KCN / mole) = 0.01628 grams of KCn
which is 16.3 mg of KCN
& rounded to the 2 sig figs which are showing in the Ka of HCN , "5.0" X 10^-10
your answer would be
16 mg of KCN
sorry even after making a correction in calcs , I don't get one of your answers.
the only way that I could get one of them is to pretend that yours was a 1 sig fig problem,
in which case your 16 mg would round off to 20 mg.
but you have 3 sig figs in "500. ml", & 2 sig figs in both the "pH of 10.00."
& The Ka of HCN = "5.0 x 10^-10."
it does however take 12 mg of NaCN, to make 500. mL of aqueous solution pH of 10.00. the molar mass of NaCN has the smaller molar mass of 49.00 grams per mole.
maybe they meant NaCN, but wrote KCN instead.
I hope i answered this correctly for you.
