Hi I just wanted to verify a few answers to chem questions I'm working on. Was wondering if anyone could help?
1. Calculate the molar concentration of 2.34g of lithium hydroxide, LiOH disolved in water to make 750ml of solution.
My answer was CLiOH = 0.133 mol/L
nLiOH = 2.34g/24g/mol = 0.0975 mol
MLiOH = 24g/mol
CLiOH = 0.1 mol/.750 ml = 0.133 mol/L
2.If 200g of glucose is present in 500ml solution, what is the w/v percentage?
my answer was 40%
200g/500ml x 100%
Were these ok?
They are ok.
Let's verify your answers step-by-step.
1. Calculate the molar concentration of 2.34g of lithium hydroxide, LiOH, dissolved in water to make 750ml of solution.
You correctly calculated the number of moles of LiOH:
nLiOH = 2.34g / 24g/mol ≈ 0.0975 mol
Next, you correctly determined the molar mass of LiOH:
MLiOH = 24g/mol
However, when calculating the molar concentration, you made a mistake. The formula for molar concentration (C) is moles of solute (n) divided by volume of solution (V) in liters:
C = n / V
You converted 750ml of solution to liters correctly (0.750 L), but you divided by 0.1 mol (which seems to be a typo), instead of 0.0975 mol:
CLiOH = 0.0975 mol / 0.750 L ≈ 0.13 mol/L (rounded to two decimal places)
So, the correct molar concentration of LiOH is approximately 0.13 mol/L, not 0.133 mol/L.
2. If 200g of glucose is present in 500ml solution, what is the w/v percentage?
You calculated the w/v percentage correctly. It is determined by dividing the mass of the solute (glucose) by the volume of the solution and multiplying by 100:
w/v % = (mass of solute / volume of solution) × 100
In this case:
w/v % = (200g / 500ml) × 100 = 40%
So, your answer of 40% is correct.
Therefore, your answer to question 2 is correct, but the answer to question 1 should be approximately 0.13 mol/L, not 0.133 mol/L.
Let's go through each question and verify your answers:
1. Calculate the molar concentration of 2.34g of lithium hydroxide, LiOH, dissolved in water to make 750ml of solution.
To determine the molar concentration (C) of LiOH, you need to divide the moles of LiOH by the volume of the solution in liters.
First, calculate the moles of LiOH (nLiOH):
nLiOH = mass / molar mass
nLiOH = 2.34g / 24.0g/mol ≈ 0.0975 mol
Next, convert the volume of the solution to liters (V):
V = 750mL = 0.750L
Finally, calculate the molar concentration:
CLiOH = nLiOH / V
CLiOH = 0.0975 mol / 0.750 L ≈ 0.13 mol/L
So, based on your calculations, the molar concentration of LiOH is approximately 0.13 mol/L. Your answer of 0.133 mol/L is very close and can be accepted as correct.
2. If 200g of glucose is present in 500ml solution, what is the w/v percentage?
To calculate the weight/volume percentage (w/v %) of glucose, divide the mass of glucose by the volume of the solution and multiply by 100.
w/v % = (mass of solute / volume of solution) × 100
Given:
Mass of glucose = 200g
Volume of solution = 500mL
Convert the volume from mL to L (for consistency):
Volume of solution = 500mL = 0.500L
Now calculate the w/v %:
w/v % = (200g / 0.500L) × 100
w/v % = 400%
Your answer of 40% is incorrect. The correct w/v percentage is 400%.