What is the molality of the solution when you have
48.2 % by mass KBr aqueous solution ?
Show each conversion step
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To find the molality of a solution, we need to know the mass of the solute (KBr) and the mass of the solvent (water).
Given:
Mass of KBr aqueous solution = 48.2%
Step 1: Convert the given percentage to grams
To convert a percentage to grams, we assume we have 100 grams of the solution. Therefore, the mass of KBr in the solution is:
Mass of KBr = 48.2 grams (100 g of solution * 48.2%)
Step 2: Calculate the moles of KBr
To calculate the moles, we need the molar mass of KBr, which is the sum of the atomic masses of potassium (K) and bromine (Br) from the periodic table.
Molar mass of KBr = atomic mass of K + atomic mass of Br
= 39.10 g/mol + 79.90 g/mol
= 119.00 g/mol
Using the molar mass, we can calculate the number of moles of KBr:
Moles of KBr = Mass of KBr / Molar mass of KBr
= 48.2 g / 119.00 g/mol
Step 3: Calculate the mass of water
To determine the mass of water, we subtract the mass of KBr from the total mass of the solution. Since we assumed we have 100 grams of solution, the mass of water is:
Mass of water = 100 g - 48.2 g
= 51.8 g
Step 4: Calculate molality
Molality is defined as the number of moles of solute (KBr) divided by the mass of the solvent (water) in kilograms.
Molality = Moles of KBr / Mass of water (in kg)
= Moles of KBr / (51.8 g / 1000)
Remember to convert the mass of water from grams to kilograms.
This gives you the molality of the solution when you have a 48.2% by mass KBr aqueous solution.