Calculate the molarity of a solution made by dissolving 12.5 grams of Na2CrO4 in enough water to form exactly 550 mL of solution. (b) How many moles of KBr are present in 150 mL of a 0.275 M solution? (c) How many milliters of 6.1 M HCl solution are needed to obtain 0.100 mol of HCl?
a) molarity= moles/liters convert grams to moles, then solve.
b) same formula, solve for moles
c) sam formula, solve for volume inliters, then convert to ml.
A .105L sample of unknown HNO3 required 46.5mL of .150M Ba(OH)2 for complete neutralization. What is concentration of HNO3
(a) To calculate the molarity of a solution, we need to use the formula:
Molarity (M) = (moles of solute) / (volume of solution in liters)
First, we need to determine the moles of Na2CrO4. The molar mass of Na2CrO4 can be calculated by adding up the atomic masses of each element:
Na = 22.99 g/mol
Cr = 52.00 g/mol
O = 16.00 g/mol (there are 4 oxygen atoms)
Molar mass of Na2CrO4 = (2 * 22.99) + 52.00 + (4 * 16.00) = 162.06 g/mol
Now, we can calculate the moles of Na2CrO4 using the given mass and molar mass:
Moles = (mass) / (molar mass) = (12.5 g) / (162.06 g/mol)
Next, we need to convert the volume of the solution from mL to liters:
Volume = 550 mL = 550 / 1000 liters = 0.550 liters
Now we can substitute the values into the molarity formula:
Molarity = Moles / Volume = (12.5 g / 162.06 g/mol) / 0.550 L
Calculating this gives us the molarity of the solution.
(b) To calculate the moles of KBr, we need to use the formula:
Moles = Molarity * Volume
Given:
Molarity = 0.275 M
Volume = 150 mL = 150 / 1000 liters = 0.150 liters
Substitute the values into the formula:
Moles = 0.275 M * 0.150 L
(c) To calculate the volume of 6.1 M HCl solution needed to obtain 0.100 mol of HCl, we can rearrange the molarity formula:
Volume = Moles / Molarity
Given:
Moles = 0.100 mol
Molarity = 6.1 M
Substitute the values into the formula:
Volume = 0.100 mol / 6.1 M
To calculate the molarity of a solution, you need to know the number of moles of solute and the volume of the solution in liters.
Let's solve the questions step by step:
(a) Calculate the molarity of a solution made by dissolving 12.5 grams of Na2CrO4 in enough water to form exactly 550 mL of solution.
1. Convert the mass of Na2CrO4 to moles. To do this, we need to know the molar mass of Na2CrO4.
- The atomic mass of Na is 22.99 g/mol.
- The atomic mass of Cr is 52.00 g/mol.
- The atomic mass of O is 16.00 g/mol.
The molar mass of Na2CrO4 = (2 * 22.99) + 52.00 + (4 * 16.00) = 161.97 g/mol.
Moles of Na2CrO4 = mass / molar mass.
Moles of Na2CrO4 = 12.5 g / 161.97 g/mol = 0.077 mol.
2. Convert the volume of the solution to liters.
Volume of the solution = 550 mL = 550/1000 = 0.55 L.
3. Calculate molarity.
Molarity (M) = moles of solute / volume of solution in liters.
Molarity = 0.077 mol / 0.55 L = 0.14 M.
Therefore, the molarity of the Na2CrO4 solution is 0.14 M.
(b) Calculate the number of moles of KBr present in 150 mL of a 0.275 M solution.
1. Convert the volume of the solution to liters.
Volume of the solution = 150 mL = 150/1000 = 0.15 L.
2. Calculate the number of moles.
Moles of solute = Molarity * Volume of solution in liters.
Moles of KBr = 0.275 mol/L * 0.15 L = 0.04125 mol.
Therefore, there are 0.04125 moles of KBr present in 150 mL of the 0.275 M solution.
(c) Calculate the number of milliliters of 6.1 M HCl solution needed to obtain 0.100 mol of HCl.
1. Calculate the volume of the solution needed.
Volume of the solution = moles of HCl / Molarity.
Volume of the solution = 0.100 mol / 6.1 mol/L = 0.0164 L.
2. Convert the volume to milliliters.
Volume in milliliters = Volume in liters * 1000.
Volume in milliliters = 0.0164 L * 1000 = 16.4 mL.
Therefore, you need 16.4 mL of 6.1 M HCl solution to obtain 0.100 mol of HCl.