Scientific Tutor

What is the ionization constant?

The ionization constant is a factor you have to take into account when you talk about splitting apart chemicals. Mostly, the ionization constant has to do with splitting apart ionic compounds. It is estimated by the number of ions you get after you break apart a chemical. While in truth, it is a little more complex than that we will go into. We will not go into that complexity here.

What is the ionization constant used for?

Most often you will see the ionization constant used with the equations having to do with the freezing point depression and boiling point elevation. Since those two concepts will be explained in the next sections, I will not go into them here. All that matters is that they relate to the formula below.

Δ T =	m * k * i
1

This is the equation for freezing point depression and boiling point elevation, but we only need to know one component of it for now. Forget about all the rest of the letters and representations. All we are going to focus on is the I. The I is the ionization constant. Do not worry about the formula because we are NOT going to use it. If you remember way back to your compounds and bonding or maybe your nomenclature lessons, there was a way you learned to take apart ionic chemical compounds. We are going to use the same skills here, but add another layer of complexity to it. Check out the Examples below.

 

VIDEO Ionization Constant Demonstrated Example 1: If you have the chemical compound CH₄ what is the ionization constant when you put it in water?

 

Step 1:

What kind of chemical is CH₄, ionic or covalent?

Answer: It is covalent (made up of all non-metals)

 

Step 2:

If it is covalent what happens to it when it encounters the water? Does it break up?

Answer: No because water is polar.

 

Step 3:

So when you put one CH₄ in how many molecules / particles / atoms do you get out?

Answer: 1

 

Step 4:

So what is the ionization constant of CH₄?

COMPLETE ANSWER: 1 = ionization constant

 

VIDEO Ionization Constant Demonstrated Example 2: If you have the chemical compound NaBr what is the ionization constant when you put it in water?

 

Step 1:

What kind of chemical is NaBr, ionic or covalent?

Answer: It is ionic (made up of metals and non-metals)

 

Step 2:

If it is ionic, what happens to it when it encounters the water? Does it break up?

Answer: Yes because water is polar.

 

Step 3:

So when you put one NaBr in how many molecules / particles / atoms / ions do you get out?

Answer: 2 (one Na⁺¹ and one Br^1-)

 

Step 4:

So what is the ionization constant of NaBr?

COMPLETE ANSWER: 2 = ionization constant

 

VIDEO Ionization Constant Demonstrated Example 3: If you have the chemical compound CaF₂ what is the ionization constant when you put it in water?

 

Step 1:

What kind of chemical is CaF₂, ionic or covalent?

Answer: It is ionic (made up of metals and non-metals)

 

Step 2:

If it is ionic what happens to it when it encounters the water? Does it break up?

Answer: Yes because water is polar.

 

Step 3:

So when you put one CaF₂ in how many molecules / particles / atoms / ions do you get out?

Answer: 3 (one Ca⁺² and two F^–)

 

Step 4:

So what is the ionization constant of CaF₂?

COMPLETE ANSWER: 3 = ionization constant

 

VIDEO Ionization Constant Demonstrated Example 4: If you have the chemical compound BaSO₄ what is the ionization constant when you put it in water?

 

Step 1:

What kind of chemical is BaSO₄, ionic or covalent?

Answer: It is ionic (made up of metals and non-metals)

 

Step 2:

If it is ionic what happens to it when it encounters the water? Does it break up?

Answer: Yes because water is polar.

 

Step 3:

So when you put one BaSO₄ in how many molecules / particles / atoms / ions do you get out?

Answer: 2 (one Ba⁺² and one SO₄^2-)

 

Step 4:

So what is the ionization constant of BaSO₄?

COMPLETE ANSWER: 2 = ionization constant

 

PRACTICE PROBLEMS: Determine what the ionization constant is for the chemicals below. Try to use a regular periodic table. However if you need you can use your metal / non-metal periodic table and your ion periodic table.

Chemical	Answer
CO2	1
RbI	2
BaF2	3
Li2O	3
FrOH	2
Ca(NO3)2	3
Ra3P2	5
Cs2CO3	3
SiH4	4