How much additional volume of solution should be added to 0.5L of a 2M oxalic acid solution in oder to decrease it concentration to 0.2M?

To decrease the concentration of the 2M oxalic acid solution to 0.2M, we need to dilute it with a certain volume of solvent (usually water).

Let V be the volume of solvent (in liters) that needs to be added to the 0.5L of 2M oxalic acid solution.

The initial moles of oxalic acid in the 0.5L of 2M solution can be calculated as:
Initial moles = initial concentration x initial volume
Initial moles = 2M x 0.5L
Initial moles = 1 mol

After dilution with V liters of solvent, the final concentration of oxalic acid will be 0.2M. The final moles of oxalic acid should remain the same as the initial moles. Therefore, we can set up the equation:

Initial moles = final concentration x (0.5L + V)
1 mol = 0.2M x (0.5L + V)

Solving for V:
1 = 0.2 x (0.5 + V)
1 = 0.1 + 0.2V
0.9 = 0.2V
V = 0.9 / 0.2
V = 4.5L

Therefore, 4.5 liters of solvent should be added to the 0.5L of 2M oxalic acid solution in order to decrease its concentration to 0.2M.

Step 1: Calculate the moles of oxalic acid in the original solution.

```
Moles of oxalic acid = Concentration (M) x Volume (L)
Moles of oxalic acid = 2 M x 0.5 L
Moles of oxalic acid = 1 mole
```

Step 2: Calculate the new concentration of the solution.

```
New concentration = 0.2 M
```

Step 3: Calculate the volume of solution required to achieve the new concentration.

```
Volume of solution = Moles of oxalic acid / New concentration
Volume of solution = 1 mole / 0.2 M
Volume of solution = 5 L
```

Step 4: Calculate the additional volume required.

```
Additional volume = New volume - Original volume
Additional volume = 5 L - 0.5 L
Additional volume = 4.5 L
```

Therefore, 4.5 L of additional solution should be added to the original 0.5 L of 2M oxalic acid solution to decrease its concentration to 0.2M.