Calculate the molarity of a solution made by dissolving 12.5 grams of Na2CrO4 in enough water to form exactly 550 mL of solution.

mols = grams/molar mass

Then M = mols/L where L = 0.550

Calculate the molarity (M) of 30.0 grams of KOH (molar mass:56.11) in 200.00 ml of solution.

To calculate the molarity of a solution, you need to know the amount of solute (in moles) and the volume of the solution (in liters).

1. Convert the mass of Na2CrO4 to moles:
The molar mass of Na2CrO4 is calculated as follows:
Na: atomic mass = 22.990 g/mol * 2 (because there are two sodium ions in Na2CrO4)
Cr: atomic mass = 51.996 g/mol
O: atomic mass = 15.999 g/mol * 4 (because there are four oxygen ions in Na2CrO4)
Molar mass of Na2CrO4 = (22.990 * 2) + 51.996 + (15.999 * 4)
Molar mass of Na2CrO4 = 161.97 g/mol

Now, we can calculate the number of moles:
Moles of Na2CrO4 = Mass of Na2CrO4 / Molar mass of Na2CrO4
Moles of Na2CrO4 = 12.5 g / 161.97 g/mol

2. Convert the volume of the solution to liters:
550 mL = 550 mL / 1000 mL/L (since there are 1000 mL in 1 L)
550 mL = 0.55 L

3. Calculate the molarity of the solution:
Molarity (M) = Moles of solute / Volume of solution
Molarity = Moles of Na2CrO4 / Volume of solution
Molarity = (12.5 g / 161.97 g/mol) / 0.55 L

Calculate the value of Molarity to get the answer.

To calculate the molarity (M) of a solution, you need to know the moles of solute and the volume of the solution in liters.

Step 1: Convert the given mass of Na2CrO4 to moles.
The molar mass of Na2CrO4 (sodium chromate) can be calculated by summing the atomic masses of its elements.
Na: 22.99 g/mol
Cr: 52.00 g/mol
O: 16.00 g/mol (x4 since there are four oxygen atoms)

Molar mass of Na2CrO4 = (22.99 x 2) + 52.00 + (16.00 x 4) = 161.97 g/mol

Moles of Na2CrO4 = mass (g) / molar mass (g/mol)
= 12.5 g / 161.97 g/mol

Step 2: Convert the given volume of the solution to liters.
Since the volume is given in milliliters (mL), we need to convert it to liters (L).
1 L = 1000 mL

Volume of solution = 550 mL / 1000
= 0.550 L

Step 3: Calculate the molarity.
Molarity (M) = Moles of solute / Volume of solution (L)

Molarity (M) = Moles of Na2CrO4 / Volume of solution (L)
= (12.5 g / 161.97 g/mol) / 0.550 L

Now, you can solve for the molarity by performing the calculation.