Question
Chemistry Question on Expressing Concentration of Solutions
A solution contains 4 g of NaOH and 16.2 g of water. The mole fraction solute and solvent are respectively
0.1, 0.9
0.2, 0.8
0.5, 0.5
0.4, 0.6
0.1, 0.9
Solution
Answer (A) 0.1, 0.9
To calculate the mole fraction of a solute and solvent in a solution, we need to determine the number of moles of each component.
Given: Mass of NaOH = 4 g Mass of water = 16.2 g
To find the number of moles of NaOH, we divide the given mass by the molar mass of NaOH. Molar mass of NaOH = 22.99 g/mol (for Na) + 16.00 g/mol (for O) + 1.01 g/mol (for H) = 39.99 g/mol Number of moles of NaOH = 4 g / 39.99 g/mol ≈ 0.1 mol
To find the number of moles of water, we divide the given mass by the molar mass of water. Molar mass of water (H₂O) = 1.01 g/mol (for H) + 1.01 g/mol (for H) + 16.00 g/mol (for O) = 18.02 g/mol Number of moles of water = 18.02 g/mol16.2 g ≈ 0.9 mol
Now, we can calculate the mole fraction of solute (NaOH) and solvent (water).
Mole fraction of solute (NaOH) = Total molesMoles of NaOH= (0.1 mol+0.9 mol)0.1 mol = 0.1
Mole fraction of solvent (water) = Total molesmoles of water = (0.1 mol+0.9 mol)0.9 mol= 0.9
Therefore, the mole fraction of solute (NaOH) and solvent (water) in the given solution are approximately 0.1 and 0.9, respectively. So the correct option is 0.1, 0.9.