What is an equivalent? | Lab values and concentrations | Health & Medicine | Khan Academy

I wanted to look up the definition of the

equivalent

word on Wikipedia. I couldn't get any useful information, but there are some points I would like to highlight. The definition of the word

equivalent

is as follows: an equivalent is the amount of substance that reacts with one mole of hydrogen ions in an acid-base reaction; or is a term that has the same function as a mole of electrons in a redox reaction. I had a hard time understanding this as I was reading it, but then I was able to determine that equivalent basically means a certain amount, a number.

Let's start right here. When someone asks how many equivalents, we must know that they are talking about numbers. For some ions, there is an equivalent that is equal to a certain number. Generally, this number is expressed in moles. To do this, you must first balance them. I balance loads. Therefore, it must have a negative charge and be monovalent. I need to add load to balance, I can add without removing. Let's look at an example to understand it more clearly. Let's take potassium. This is our potassium. We need to balance one mole of 1 negatively charged valence element.

I draw such a small line to separate the sides. On the other side I write chloride. Chloride is exactly the opposite. It is negatively charged. 1 valence. It's not minus 2 or minus 3, it's minus 1. Let's call them moles, it takes 1 mole of negative charge. There is no other way. No way, okay? So let's solve the problem, let's say here: we multiply 6.02, there are 23 chlorides out of 10. The question is how much total potassium is needed to balance the charge of these chlorides. This is a very large number, so we need to find the mole of potassium. I have shown it here in the definition.

Now let's define. A potassium combines with a chloride. We know it is. Potassium collides with chloride and combines in a one-to-one ratio. We have determined that a potassium is reduced to a chloride. That is, to combine one mole of chloride you need one mole of potassium. This completely balances the load. How many potassium equivalents? one might ask. The answer is very simple. We answer that one mole of potassium has an equivalent. You can express it another way. You can say that 1 mole of potassium is equal to 1 equivalent, which is the definition that people usually give. They both have the same meaning.

Let's look at a slightly more difficult example, you will see that it is a little different. This time, instead of potassium, we took another. Let's make calcium. It is positive two in calcium. We will do the same again. We must choose a 1-valent element with a negative charge. Since it has a negative charge, I can also take the same item. It must have a negative charge and 1 valence, chloride fits. As before, this time we need to know the mole. We need to determine how much calcium will combine with the chloride, or vice versa, how many chlorides will combine with the calcium?

What happens when calcium and chloride meet? Here there is chloride and here there is calcium. He will come here. Here they will combine and form said substance. This substance is called calcium chloride, the charge of chlorine is negative 1 and the charge of calcium is positive 2. I put negatives and positives. I apologize for that. We continue. Negative, negative, this is positive 2. For every calcium, 2 chlorides fall. Let's write more clearly. 1 calcium corresponds to 2 chlorides. If I divide each side in half, 0.5 of calcium becomes 1 of chloride. However, 0.5 calcium is difficult to calculate. We can simplify this mathematically. 1 mole of chloride corresponds to 0.5 mole of calcium.

This is how we write. In this case, 1 equivalent is equivalent to 0.5 mol of calcium. Let's make some changes to the equation. We multiply each side by two, 1 mole of calcium is equivalent to 2 equivalents. It is usually displayed this way. How much is equivalent to 1 mole of substance? The answer here is 2. We took the long way, but there is a shorter way. Calcium has a valence of 2 and potassium has a valence of 1, which is an interesting example. Since calcium has a positive charge of 2, it has 2 equivalents. Now let's check with a trivalent element. Let's take nitrogen. Let's make nitrogen.

The charge on nitrogen is negative 3. To do this, on the opposite side there must be a monovalent element with an opposite charge. That is, we must choose an element with valence 1 and positive charge. Let's choose. Fits. Of this we need 1 mole. As we mentioned above, there is no other way. Suppose there is 1 mole of this. How much nitrogen is needed to balance? I draw a red line under the 3. This is a clue. Let's try to determine this to a large extent. Let's say we have nitrogen here, it has a negative 3 charge and it will encounter protons. 3 of them come forward.

NH3 is formed here. Let's say 3 protons meet 1 nitrogen, then we divide each side by 3, 1 proton is equal to 1 nitrogen in 3, we get that equation. We're still fine. It takes 1 mole of nitrogen in 3 to balance 1 mole of protons. That is, 1 equivalent is equal to 1 mole of nitrogen in 3. As we did before, we will make a change here. We said that 1 mole of nitrogen means 3 equivalents. We already underlined these 3 and we do it again. Here you can clearly follow the pattern. Suppose magnesium is given, the charge of elements like magnesium and calcium is positive 2, we can determine the equivalent number by doing

what

we just did, and the equivalent will be the same number.

Nitrogen has 3 equivalents. Magnesium or calcium have 2. Potassium and elements such as chloride have 1. We conclude that the equivalent is the number of moles necessary to balance the charges on the opposite side.