To prepare a 1 M solution of phosphoric acid from 85% phosphoric acid, we will need to carefully calculate the amounts of phosphoric acid and water to mix together. Let's break down the process step by step.
1. Determine the volume needed: In this case, we want to prepare 500 ml of the 1 M solution. So, we have our target volume established.
2. Calculate the amount of phosphoric acid required: Since we are working with an 85% concentration of phosphoric acid, we need to calculate how much of it we should mix with water. To do this, we can use the formula:
Volume of phosphoric acid (ml) = (Desired concentration / Actual concentration) * Volume of solution (ml)
Plugging in the values, we get:
Volume of phosphoric acid (ml) = (1 M / 0.85 M) * 500 ml
Volume of phosphoric acid (ml) = 588.24 ml
Therefore, we need to measure out approximately 588.24 ml of the 85% phosphoric acid.
3. Calculate the amount of water required: Now that we know how much phosphoric acid to use, we can calculate the amount of water needed to make up the remaining volume. This can be done by subtracting the volume of phosphoric acid from the total volume:
Volume of water (ml) = Volume of solution (ml) – Volume of phosphoric acid (ml)
Volume of water (ml) = 500 ml – 588.24 ml
Volume of water (ml) = -88.24 ml
Wait, a negative volume of water? That doesn't make sense in this context. Negative volumes typically arise when the initial concentration is higher than the desired concentration, and we need to dilute the solution. However, in this case, we already have a dilute solution (85%) and want to make it more concentrated (1 M). So, it seems we made a mistake in our calculations.
4. Recalculate the amount of phosphoric acid required: Let's correct the error by recalculating the amount of phosphoric acid needed. Since we want to prepare a 1 M solution, we can use the formula:
Volume of phosphoric acid (ml) = Desired concentration * Volume of solution (ml)
Volume of phosphoric acid (ml) = 1 M * 500 ml
Volume of phosphoric acid (ml) = 500 ml
Therefore, we need to measure out exactly 500 ml of the 85% phosphoric acid.
5. Recalculate the amount of water required: With the correct amount of phosphoric acid determined, we can now calculate the volume of water needed to achieve our desired solution:
Volume of water (ml) = Volume of solution (ml) – Volume of phosphoric acid (ml)
Volume of water (ml) = 500 ml – 500 ml
Volume of water (ml) = 0 ml
This means we don't need to add any water to the phosphoric acid since we want a concentrated solution.
In summary, to prepare 500 ml of a 1 M phosphoric acid solution from 85% phosphoric acid, we need to measure out 500 ml of the 85% phosphoric acid without adding any water. It's essential to double-check our calculations to avoid errors and ensure the accuracy of the final solution.