Please help.
Concentrated hydrochloric acid is a 38% w/w solution of HCL in water and has a density of 1.18g/ml. How many millilitres of concentrated hydrochloric acid are needed to prepare 500ml of a 1:200 w/v HCL solution?
My answer is 2.12ml. I'm not sure if its correct. Please help.
Frankly, I don't know what 1:200 w/v HCl means.
1:200 w/v means 1g in 200ml
To solve this problem, we need to calculate the volume of the concentrated hydrochloric acid required to prepare a 1:200 w/v HCL solution.
Let's start by understanding what a 1:200 w/v HCL solution means. This ratio indicates that for every 1 part of the solute (HCL), there are 200 parts of the solvent (water). In this case, the solute is the concentrated hydrochloric acid (38% w/w HCL solution) and the solvent is water.
1. Calculate the mass of HCL in the 500 ml 1:200 w/v HCL solution:
Since the ratio is by volume (w/v), we need to convert the volume of the solution (500 ml) into grams.
Density = Mass / Volume.
Mass = Density * Volume.
Mass = 1.18 g/ml * 500 ml = 590 g.
2. Determine the mass of HCL in the 1:200 w/v solution:
Since the HCL solution is 1:200 w/v, it means there are 1/201 parts of the solute (HCL) for every 201 parts of the solution.
Therefore, the mass of HCL = (1/201) * Total Mass of the Solution.
Mass of HCL = (1/201) * 590 g.
Mass of HCL ≈ 2.93 g.
3. Calculate the mass of HCL in the concentrated hydrochloric acid:
The 38% w/w solution means that 38 g of HCL is present in 100 g of the solution.
Therefore, the mass of HCL in the concentrated acid = (38/100) * Total Mass of the Solution.
Mass of HCL in the concentrated acid = (38/100) * X g, where X is the total mass of the concentrated hydrochloric acid.
4. Equate the mass of HCL in the 1:200 w/v solution and the concentrated acid:
(38/100) * X = 2.93 g.
Solving for X: X ≈ 7.7 g.
5. Calculate the volume of the concentrated hydrochloric acid needed:
Density = Mass / Volume.
1.18 g/ml = 7.7 g / Volume.
Solving for Volume: Volume ≈ 6.53 ml.
Therefore, approximately 6.53 ml of concentrated hydrochloric acid is needed to prepare 500 ml of a 1:200 w/v HCL solution.
Your answer of 2.12 ml seems incorrect. The correct answer is approximately 6.53 ml.