How would set up a problem like this?
A mass of 20.0 g of NaOH is dissolved in water to form 5.0 dm^3 of solution. What is the molarity of the hydrogen ion concentration if the temperature is 25 degrees Celsius?
M = #moles/dm^3
moles = grams/molar mass
Solve for moles.
Substitute moles and dm^3 to find M. Then
pOH = -log(OH^-) and solve for pOH.
Then pOH + pH = 14 and solve for pH.
3
To set up this problem, we need to determine the molarity of the hydrogen ion concentration in the NaOH solution. Here are the steps to follow:
1. Write down the balanced chemical equation for the ionization of NaOH in water:
NaOH (s) → Na+ (aq) + OH- (aq)
2. Calculate the number of moles of NaOH used in the solution:
Moles of NaOH = mass of NaOH / molar mass of NaOH
The molar mass of NaOH can be determined by adding the atomic masses of Na, O, and H:
Molar mass of NaOH = atomic mass of Na + atomic mass of O + atomic mass of H
3. Convert the volume of the solution in liters:
Volume of solution = 5.0 dm^3 = 5.0 liters
4. Since NaOH completely ionizes in water, we know that the quantity of OH- ions will be equal to the moles of NaOH used. Therefore, you can establish a 1:1 ratio between the moles of NaOH and the moles of OH- ions.
5. Next, we need to determine the concentration of OH- ions, which is the same as the concentration of NaOH, as they both have a 1:1 relationship:
Molarity of OH- = moles of OH- ions / volume of solution
6. Since water ionizes into H+ and OH- ions in equal amounts, the concentration of H+ ions will also be equal to the concentration of OH- ions, meaning the molarity of H+ is the same as the molarity of OH-.
Therefore, the molarity of the hydrogen ion concentration in the NaOH solution is equal to the molarity of the hydroxide ion concentration, which can be calculated using the above steps.