Answer:
Only the number of neutrons change.
The idea here is that you need to figure out how many moles of magnesium chloride,
MgCl
2
, you need to have in the target solution, then use this value to determine what volume of the stock solution would contain this many moles.
As you know, molarity is defined as the number of moles of solute, which in your case is magnesium chloride, divided by liters of solution.
c
=
n
V
So, how many moles of magnesium chloride must be present in the target solution?
c
=
n
V
⇒
n
=
c
⋅
V
n
=
0.158 M
⋅
250.0
⋅
10
−
3
L
=
0.0395 moles MgCl
2
Now determine what volume of the target solution would contain this many moles of magnesium chloride
c
=
n
V
⇒
V
=
n
c
V
=
0.0395
moles
3.15
moles
L
=
0.01254 L
Rounded to three sig figs and expressed in mililiters, the volume will be
V
=
12.5 mL
So, to prepare your target solution, use a
12.5-mL
sample of the stock solution and add enough water to make the volume of the total solution equal to
250.0 mL
.
This is equivalent to diluting the
12.5-mL
sample of the stock solution by a dilution factor of
20
.
Answer:
[Cl-18]⁻ & [Cl-20]⁻
Explanation:
By definition isotopes are elements with the same number of protons by different number of neutrons. Elements X-18 & X-20 have 17 protons and represent Chlorine isotopes Cl-18 & Cl-20 each with 17 protons and 18 electrons to give the isotopes a -1 oxidation state. Both isotope of chlorine have 7 electron in its valence shell and 10 electrons in its core structure. Gaining 1 electron fills the valence octet and establishes a -1 oxidation state.