can you check if I did the problems correctly? thanks!
a soln of NaOH is prepared by dissolving 5.0g of NaOH in 500mL of water, the nadding additional water to make 1.0 L of soln. What is the pOH and pH of this soln?
[OH-]=(5g/40g)mol/1L
pOH=-log(1/8)=.90
[H3O+]=(1.0x10^-14)/(1/8)=8x10^-14
pH=-log(8x10^-14)=13.10
What is true about strong acids and bases?
*It is impossible to calculate pH from the hydroxide ion concentration
*pOH is not related to the proton concentration
*the concentration of hydroxide ions or proton is equal to the concentration of the substance dissolved
*pOH is equal to -pH
Statement 1 is wrong in saying that it is "impossible" I could also eliminate statement 4. I think either statement 2 or 3 is correct. Which one is it?
The pH of the NaOH solution is done correctly and you have the correct answer.
Problem 2.
Statement 1 definitely is not true.
Statement 2 definitely is not true (you just did that in the problem above).
Statement 3 is true.
Statement 4 definitely is not true for you used that in the problem above.
To check if you did the problems correctly, let's go through the calculations step by step.
First, let's calculate the concentration of hydroxide ions ([OH-]) in the solution.
Given:
Mass of NaOH = 5.0g
Molar mass of NaOH = 40g/mol
Volume of water = 500mL = 0.5L
[OH-] = (5g/40g) mol / 1L
[OH-] = 0.125 mol/L
Now, let's calculate the pOH of the solution.
pOH = -log([OH-])
pOH = -log(0.125)
pOH ≈ 0.90
Next, let's calculate the concentration of hydronium ions ([H3O+]) in the solution. Since NaOH is a strong base, it dissociates completely in water to produce equal amounts of OH- and H3O+ ions. Therefore, the concentration of [H3O+] is equal to the concentration of [OH-].
[H3O+] = [OH-]
[H3O+] ≈ 0.125 mol/L
Finally, let's calculate the pH of the solution.
pH = -log([H3O+])
pH = -log(0.125)
pH ≈ 0.90
Based on your calculations, it seems like there was a mistake in determining the pOH and pH values. Note that for a solution of NaOH, pOH and pH should be equal since it is neutral. So, to clarify:
Correct calculation:
pOH ≈ 0.90
pH ≈ 0.90
Now, let's address your question about true statements regarding strong acids and bases.
Statement 1: It is impossible to calculate pH from the hydroxide ion concentration. - This statement is incorrect. You can calculate the pH from the hydroxide ion concentration, as shown in the calculations above.
Statement 2: pOH is not related to the proton concentration. - This statement is incorrect. pOH is related to the hydroxide ion concentration, which is indirectly related to the proton concentration.
Statement 3: The concentration of hydroxide ions or protons is equal to the concentration of the substance dissolved. - This statement is correct. In a strong acid or base solution, the concentration of hydroxide ions or protons is essentially equal to the concentration of the acid or base dissolved.
Statement 4: pOH is equal to -pH. - This statement is incorrect. In the case of a neutral solution, pOH and pH should be equal, but in general, pOH is not equal to -pH.
Based on the correct statements, it seems like Statement 3 is the correct one.
Correct statement: The concentration of hydroxide ions or protons is equal to the concentration of the substance dissolved.
I hope this helps clarify your calculations and answer your question! Let me know if you have any further inquiries.