What is the pH of the following solutions?
1)a solution that is 5.4×10−2 M in HClO4 and 3.0×10−2 M in HCl
2)a solution that is 1.80% HCl by mass (Assume a density of 1.01g/mL for the solution.)
Please help! I am so confused!
HClO4 is a strong acid. HCl (solution) is a strong acid. Calculate moles L H^+ in each, add them together for total moles H^+.
How much does a L weigh?
1000 mL x 1.01 g/mL = 1010 grams.
How much HCl does that contain? 1.8%; therefore,
1010 x 0.018 = ?? grams HCl.
How many moles is that?
moles = grams/molar mass = xx moles. That is in 1 L therefore, that is the molarity. It's a strong acid so that must be the H^+ in moles/L. Calculate pH from that.
Thanks for your help! I understand number 2, but I still don't get number 1. Is there any other way to explain it?
For #1, let's make things simpler by using different molarities and different acids. I think the small numbers make the waters murky. Suppose we had 1 L of a solution that was 1 molar in HCl and 1 M in HCl. (I know that's the same acid but play along with me.) So the total H^+ must be 2 M. It's 1 mole/L from the first HCl and it's 1 mole/L from the second HCl, right. So 1 mole/L from the first acid + 1 moles/L from the second acid makes 2 moles/L from both of them. Now we change that to 1 M in HCl and 1 M in HClO4. The H^+ is a H^+. All of the H^+ look alike.They don't know they came from different sources. So the H^+ is 1 M from HCl and it is 1 M from HClO4 (that's a strong acid, too, and ionizes completely). So the total H^+ is 1 + 1 = 2 M. The Cl^- is only 1 M and the ClO4^- is only 1 M but the H^+ is 2 M. Is the total + charge = total - charge. Yes. 2M + ions and 2M negative ions.
THANK YOU!
To find the pH of a solution, you need to know the concentration of H+ ions. I will guide you through the process of finding the pH for each of the given solutions.
1) Solution that is 5.4×10−2 M in HClO4 and 3.0×10−2 M in HCl:
a) For HClO4: HClO4 is a strong acid that fully ionizes in water. This means that the concentration of H+ ions is equal to the concentration of the acid itself. So, the concentration of H+ ions in this solution is 5.4×10−2 M.
b) For HCl: Similarly, HCl is also a strong acid. Therefore, the concentration of H+ ions is equal to the concentration of the acid. In this case, it is 3.0×10−2 M.
c) Now, to find the total concentration of H+ ions in the solution, you need to add the individual concentrations of H+ ions from HClO4 and HCl together:
Total concentration of H+ ions = Concentration of H+ ions from HClO4 + Concentration of H+ ions from HCl
= 5.4×10−2 M + 3.0×10−2 M
= 8.4×10−2 M
d) Finally, to find the pH, use the equation: pH = -log[H+]
pH = -log(8.4×10−2)
Using a calculator, you can find that the pH is approximately 1.08.
2) Solution that is 1.80% HCl by mass:
a) To find the concentration of HCl in this solution, you need to convert the percent mass to molarity. First, you calculate the mass of HCl in the solution. Assume you have 100 grams of the solution, so 1.80% of 100 grams is 1.8 grams.
b) Next, you need to convert the mass of HCl to moles by dividing the mass by the molar mass of HCl. The molar mass of HCl is 36.46 g/mol.
Number of moles of HCl = 1.8 g / 36.46 g/mol
c) Now, you need to find the volume of the solution. Assume you have 100 mL (or 0.1 L) of the solution since the density is given as 1.01g/mL.
d) Finally, to find the molarity, divide the number of moles of HCl by the volume of the solution in liters:
Molarity of HCl = Number of moles of HCl / Volume of solution in liters
Molarity of HCl = (1.8 g / 36.46 g/mol) / 0.1 L
Using a calculator, you can find the molarity of HCl in this solution.
Once you have the molarity, you can follow the steps mentioned in the first example to find the pH by using the equation pH = -log[H+].
I hope this explanation helps you understand how to find the pH of these solutions. Let me know if you have any further questions!