# chem

posted by .

1. What is the [K+] of a solution prepared by dissolving 0.140 g of potassium hydroxide in
sufficient pure water to prepare 250.0 ml of solution?

2. What is the pH of a 0.570 M solution of aniline? Kb = 7.4 × 10-10

• chem -

Convert 0.140 g KOH to mols. mols = grams/molar mass.
There is 1 mol K^+ per mol KOH.
Then [K^+] = mols/0.250 L = ??

Let's designate, for simplicity in typing, aniline as RNH2.
RNH2 + HOH ==> RNH3^+ + OH^-
Kb = (RNH3^+)(OH^-)/(RNH2) = 7.4 x 10^-10
(RNH3^+) = x
(OH^-) = x
(RNH2) = 0.570 - x
Substitute into Kb and solve for x = (OH^-), convert to (H^+) and solve for pH. Post your work if you get stuck.
Check my thinking.

## Similar Questions

1. ### Chem I

Calculate the concentrations of hydronium and hydroxide ions in a solution prepared by dissolving 0.345g of solid NaOH in enough water to make 225mL of solution. Also calculate the pH and pOH of the solution.
2. ### Chemistry

A student makes a solution by dissolving 55.8 grams of potassium hydroxide in 875.0 grams of water. The resulting solution has a density of 1.07 grams per milliliter. 1. What is the volume of this solution?
3. ### Chemistry

A student makes a solution by dissolving 55.8 grams of potassium hydroxide in 875.0 grams of water. The resulting solution has a density of 1.07 grams per milliliter. 1. What is the volume of this solution?
4. ### Chemistry

A student makes a solution by dissolving 55.8 grams of potassium hydroxide in 875.0 grams of water. The resulting solution has a density of 1.07 grams per milliliter. 1. What is the volume of this solution?
5. ### Chemistry

A student makes a solution by dissolving 55.8 grams of potassium hydroxide in 875.0 grams of water. The resulting solution has a density of 1.07 grams per milliliter. 1. What is the volume of this solution?
6. ### Chemistry- Drbob-help

I have placed the answer I got please help. A student makes a solution by dissolving 55.8 grams of potassium hydroxide in 875.0 grams of water. The resulting solution has a density of 1.07 grams per milliliter. 1. What is the volume …
7. ### CHEM

What is the molarity of potassium iodide solution prepared by adding 5.810g of KI to sufficient water to make a final solution volume of 250.0mL?
8. ### chemistry

A solution is prepared by mixing 4.62 grams of potassium hydroxide in 1.00 L of water. After that, 250.0 mL of a 0.100 M solution of HCl is added to the solution. What is the resulting pH of the final mixture?
9. ### chem

A solution is prepared by dissolving 15.0 g of pure HC2H3O2 and 15.0 g of NaC2H3O2 in 600 mL of solution (the final volume). What is the pH of the solution?
10. ### science chemistry

Brandon prepares a potassium hydroxide solution (KOH) that he uses during a titration to determine the unknown concentration of a hydrochloric acid solution calculate the mass of potassium hydroxide that is need to prepare 250 cm^3 …

More Similar Questions