An aqueous solution labelled 35.0% w/w HClO4 has a density of 1.251 g cm¯3. What is the molarity of the solution?
My answer is 0.436 (3dp). Can someone check this please. Thanks
Thank you
To find the molarity (M) of the solution, we first need to convert the weight percentage (w/w) to grams of solute per liter of solution. Here are the steps to calculate it:
Step 1: Assume we have 100 grams of the solution (since weight percentage is given).
Step 2: In 100 grams of the solution, there are 35 grams of HClO4 (35% w/w).
Step 3: Now we need to convert the grams of HClO4 to moles.
The molar mass of HClO4 (chloric acid) is:
H = 1.0079 g/mol x 1 = 1.0079 g/mol
Cl = 35.453 g/mol x 1 = 35.453 g/mol
O = 16.00 g/mol x 4 = 64.00 g/mol
Total molar mass of HClO4 = 1.0079 + 35.453 + 64.00 = 100.46 g/mol
Now, using the molar mass, we can calculate the number of moles of HClO4:
moles = mass / molar mass
moles = 35 g / 100.46 g/mol ≈ 0.3487 mol (4dp)
Step 4: Now we need to convert the volume of the solution in liters.
The density of the solution is given as 1.251 g/cm³.
As density = mass / volume, we can rearrange the equation to find the volume:
volume = mass / density
volume = 100 g / 1.251 g/cm³ = 79.9361 cm³ (4dp)
Since 1 cm³ is equal to 1 mL, 79.9361 cm³ is equal to 79.9361 mL.
Converting mL to liters:
volume = 79.9361 mL / 1000 mL/L = 0.0799 L (4dp)
Step 5: Now, we can calculate the molarity using the formula:
Molarity (M) = moles / volume
M = 0.3487 mol / 0.0799 L ≈ 4.360 (3dp)
Hence, the molarity of the solution is approximately 4.360 M, not 0.436 M.
To find the molarity of the solution, you need to know the molar mass of HClO4.
HClO4 consists of hydrogen (H), chlorine (Cl), and oxygen (O).
Hydrogen has an atomic mass of approximately 1 g/mol, chlorine has an atomic mass of approximately 35.5 g/mol, and oxygen has an atomic mass of approximately 16 g/mol.
To calculate the molar mass of HClO4, you need to add up the atomic masses of each element based on their respective ratios in the formula. In this case, the ratio is 1:1:4 for H:Cl:O.
So, the molar mass of HClO4 is:
1(1 g/mol) + 1(35.5 g/mol) + 4(16 g/mol) = 1 + 35.5 + 64 = 100.5 g/mol.
The solution is labeled as 35.0% w/w HClO4, which means that 35.0 g of HClO4 is present in 100.0 g of the solution.
To convert this into moles, divide the mass of HClO4 by its molar mass:
moles of HClO4 = mass of HClO4 / molar mass of HClO4
moles of HClO4 = 35.0 g / 100.5 g/mol
Now, we need to determine the volume of the solution.
The density of the solution is given as 1.251 g/cm^3. Density is defined as mass divided by volume:
density of the solution = mass of the solution / volume of the solution
Rearranging the equation, we can solve for the volume:
volume of the solution = mass of the solution / density of the solution
volume of the solution = 100.0 g / 1.251 g/cm^3
Now that we have the moles of HClO4 and the volume of the solution, we can calculate the molarity:
molarity (M) = moles of solute / volume of solution in liters
molarity (M) = (moles of HClO4) / (volume of the solution in mL x 0.001 L/mL)
Substituting the values, we have:
molarity (M) = (35.0 g / 100.5 g/mol) / (100.0 g / 1.251 g/cm^3 x 0.001 L/mL)
Calculating this, we get:
molarity (M) ≈ 0.434 M
Therefore, the molarity of the solution is approximately 0.434 M, not 0.436 M as you stated.
Please note that the final answer is rounded to three decimal places to match your requested format.
consider a liter of the solution. Its mass: 1.251kg. Mass of HClO4= .35 x 1251gram= 487grams
Moles= 487/105=4.64moles
Molarity=4.64
check my thinking,we are way off in agreement.