Describe how to prepare 1 liter of 0.5N solution of HCl from concentrated HCl. H=1, Cl=35.5, spgr=1.19, 37.2%
Find the normality (molarity of HCl is the same as normality).
mass HCl in 1 L soln = 1.19g/mL x 1000 mL x 0.372 = 442.68 g.
How many moles is that?
442.68/36.5 = 12.12 N
Then mL x N = mL x N
mL x 12.12 = 1000 mL x 0.5N
Solve for mL of the concd acid.
Problems stated like this usually have a trick to them and many students never realize it. Here is the trick part. You solve for the mL of the concd acid, place that # mL in a 1 L volumetric flask, then add water TO THE MARK OF THE FLASK. [Note: This is NOT the same as placing 41.25 mL of the concd acid in a container and adding 958.75 mL water.]
Second note: The problem as you wrote it has only one significant figure (in the 0.5 N solution) and you should round the answer to just one s.f. unless you omitted some zeros from the 0.5N figure.
To prepare a 1-liter solution of 0.5N HCl from concentrated HCl (37.2%), you can follow these step-by-step instructions:
Step 1: Write down the formula of HCl
- The formula of HCl consists of one hydrogen (H) atom and one chlorine (Cl) atom.
Step 2: Determine the molar mass of HCl
- HCl has a molar mass of 1 (mass of H) + 35.5 (mass of Cl) = 36.5 g/mol.
Step 3: Calculate the volume of concentrated HCl needed
- You want to prepare a 1-liter solution, so you need 1 liter of the final solution.
- The specific gravity (spgr) of the concentrated HCl is given as 1.19, which means it is 1.19 times as dense as water.
- Thus, you will need 1/1.19 = 0.8403 liters (840.3 mL) of concentrated HCl solution.
Step 4: Determine the amount of HCl in moles
- The concentration of the final solution is given as 0.5N, which represents the molarity (moles per liter).
- Therefore, you need 0.5 moles of HCl in 1 liter of the final solution.
Step 5: Calculate the mass of HCl needed from the moles
- The mass of 0.5 moles of HCl can be calculated using the molar mass:
Mass = 0.5 mol × 36.5 g/mol = 18.25 grams
Step 6: Determine the volume of concentrated HCl needed
- To calculate the volume of 37.2% HCl solution required, you need to know its concentration in terms of mass/volume (g/mL).
- The given concentration (37.2%) means that 100 mL of HCl contains 37.2 grams of HCl.
- Convert the mass (gram) to volume (mL):
Volume = (18.25 g) / (37.2 g/mL) = 0.4914 L (491.4 mL)
Step 7: Dilute the concentrated HCl to make 1 liter of 0.5N HCl solution
- Take a suitable container (measuring cylinder or beaker) and add approximately 840.3 mL of concentrated HCl solution.
- Add distilled water to reach the final volume of 1 liter (1000 mL).
- Mix well to ensure uniformity.
Note: It is important to handle concentrated HCl with caution, as it is corrosive and can cause severe burns. Please follow proper safety protocols and wear appropriate protective equipment when working with chemicals.
To prepare a 1 liter solution of 0.5N HCl from concentrated HCl, you will need to follow a few steps:
Step 1: Determine the molecular weight of HCl
HCl consists of one atom of hydrogen (H) with a molecular weight of 1 and one atom of chlorine (Cl) with a molecular weight of 35.5. Add them together to get the molecular weight of HCl, which is 36.5.
Step 2: Determine the number of moles of HCl needed
The normality (N) of a solution is defined as the number of equivalents of solute per liter of solution. In this case, we want a 0.5N solution of HCl. Since the molecular weight of HCl is 36.5, a 0.5N solution would contain 0.5 equivalents of HCl per liter.
Step 3: Calculate the volume of concentrated HCl required
To calculate the volume of concentrated HCl required, you need to know its concentration and density. From the information provided, you mentioned that the concentrated HCl has a specific gravity (spgr) of 1.19 and is 37.2% HCl.
First, you need to calculate the molarity of the concentrated HCl solution. Since 37.2% of the solution is HCl, this means that 1000 ml of the solution contains 372 ml of HCl.
To convert the volume of HCl to moles, divide the volume in milliliters by the density of the solution. The density is given by the specific gravity (spgr) multiplied by the density of water (1 g/ml) which is 1.19 g/ml.
Let's calculate the moles of HCl:
372 ml of HCl / (1.19 g/ml) = 312.18 g of HCl
312.18 g of HCl / 36.5 g/mol (molecular weight of HCl) = 8.55 mol of HCl
So, you would need 8.55 moles of concentrated HCl to prepare a 1 liter solution of 0.5N HCl.
Step 4: Dilute the concentrated HCl to prepare the desired solution
To prepare the 0.5N solution, take the calculated moles of concentrated HCl (8.55 mol) and add water to make the total volume of 1 liter. You can use a volumetric flask or any other suitable container to mix the solution.
Note: When diluting concentrated acids, always remember to add the acid to water slowly while stirring. This is to avoid any heat generation or splashing that may occur due to the exothermic reaction.
By following these steps, you can prepare a 1 liter solution of 0.5N HCl using concentrated HCl.