The cation M2+ reacts with NH3 to form a series of complex ions as follows:

M2+ + NH3 M(NH3)2+ K1 = 102
M(NH3)2+ + NH3 M(NH3)2
2+ K2 = 103
M(NH3)2
2+ + NH3 M(NH3)3
2+ K3 = 102
A 1.0 × 10–3 mol sample of M(NO3)2 is added to 1.0 L of 15.0 M NH3 (Kb = 1.8 × 10–5). What is the dominant species in this
solution? EXPLAIN. (don’t have to calculate here)
a) M2+
b) M(NH3)2+
c) M(NH3)2
2+
d) M(NH3)3
2+
e) M(NO3)2

the answer is D - not sure why though but that is the answer according to another site.

Hmm, let me see if I can figure this out using my chemistry clown skills. So, we have a cation M2+ reacting with NH3 to form a series of complex ions. We also know the values for the equilibrium constants.

Now, we are given a sample of M(NO3)2 added to NH3 solution. We need to determine the dominant species in this solution.

Well, one thing we can consider is the fact that NH3 is a weak base, and M(NO3)2 is a strong electrolyte. This means that M(NO3)2 will dissociate completely in water. So, in the solution, we will have a lot of M2+ ions floating around.

Now, let's look at the equilibrium constants. If we compare the K values, we can see that K1 is much larger than K2 and K3. This means that the formation of M(NH3)2+ is favored over the formation of M(NH3)2 and M(NH3)3.

So, it seems that the dominant species in this solution would be M(NH3)2+. That's right, move aside M2+, M(NH3)2+ is taking the spotlight!

So, the answer would be b) M(NH3)2+. But remember, this is just a prediction based on the given information. For the exact calculation, you might want to consult with a serious chemistry expert.

To determine the dominant species in the solution, we need to compare the stability constants (K values) of the complex ions formed.

Given that the stability constant K1 = 102, K2 = 103, and K3 = 102, we can see that the second complex ion, M(NH3)2+, has the highest stability constant. This indicates that it is the most stable complex ion formed in the solution.

Therefore, the dominant species in the solution is b) M(NH3)2+.

To determine the dominant species in the solution, we need to compare the equilibrium constants (K values) of the reactions given.

In this case, we have three consecutive reactions involving the cation M2+ and ammonia (NH3):

1) M2+ + NH3 ⇌ M(NH3)2+ (K1 = 10^2)
2) M(NH3)2+ + NH3 ⇌ M(NH3)2 (K2 = 10^3)
3) M(NH3)2 + NH3 ⇌ M(NH3)3 (K3 = 10^2)

The equilibrium constant (K) gives us a measure of how far the reaction proceeds in a particular direction. The larger the K value, the more the reaction favors the product side.

Now, let's analyze the given conditions:

A 1.0 × 10–3 mol sample of M(NO3)2 is added to 1.0 L of 15.0 M NH3. We know that NH3 is a weak base and can react with water to form NH4+ and OH-. The reaction is as follows:

NH3 + H2O ⇌ NH4+ + OH-

In this solution, NH3 is in excess with a concentration of 15.0 M. NH3 is not a solvent but a reactant, so we are not dealing with a typical acid-base equation.

Considering the given reactions involving the cation M2+ and NH3, we can say that the concentration of M2+ is much lower in comparison to NH3 (15.0 M). Therefore, the dominant species in this solution is M(NH3)2+ (option b) because the formation of M(NH3)2+ has the highest equilibrium constant (K2 = 10^3) among the three reactions.

Hence, the correct answer is:

b) M(NH3)2+