Determine the molarity of 30% (w/w) KOH of specific gravity 1.29. Thanks for any help.
Take a liter of solution.
1.29 g/mL x 1000 mL = 1290 g.
Part is water and part is KOH. The KOH is 30%; therefore,
1290 x 0.3 = ?? grams KOH.
Determine mols KOH and that is mols/L and that is molarity.
To determine the molarity of a 30% (w/w) KOH solution, we need to convert the weight percent to moles per liter (Molarity). Here's how you can calculate it step by step:
Step 1: Convert the weight percent to grams.
- Assume you have 100g of the solution. Since it is a 30% (w/w) KOH solution, 30g of KOH is present.
Note: "w/w" means weight percent, i.e., the weight of KOH is 30% of the total weight of the solution.
Step 2: Determine the moles of KOH.
- Find the molar mass of KOH (potassium hydroxide). It is the sum of the atomic masses of potassium (K), oxygen (O), and hydrogen (H).
- Molar mass of K = 39.10 g/mol
- Molar mass of O = 16.00 g/mol
- Molar mass of H = 1.01 g/mol
- The molar mass of KOH = (39.10 + 16.00 + 1.01) g/mol = 56.11 g/mol
- Now, divide the mass of KOH in grams by its molar mass to obtain the moles of KOH.
- Moles of KOH = (mass of KOH in grams) / (molar mass of KOH)
Step 3: Determine the volume of the solution in liters.
- The specific gravity of 1.29 indicates the density of the solution relative to water.
- Assume you have 1 liter (1000 mL) of the solution. The density of water is approximately 1 g/mL.
- Since the specific gravity is 1.29, the density of the solution is 1.29 g/mL.
- The mass of 1 liter (1000 mL) of the solution is 1.29 kg (1.29 x 1000 g).
Note: density (g/mL) x volume (mL) = mass (g)
Step 4: Calculate the molarity.
- Molarity (M) is defined as moles of solute per liter of solution.
- Divide the moles of KOH obtained in step 2 by the volume of the solution in liters (as obtained in step 3).
- Molarity (M) = (moles of KOH) / (volume of the solution in liters)
Now, you can substitute the values from your question into the above steps to get the result.