Please help me.
1. A chemist adds 25.0 mL of a 43.4 g/dL iron (ii) bromide (FeBr2) solution to a flask. Calculate the mas in gram of iron (ii) bromise the chemist has added to the flask.
2. A certain substance X has a normal boiling point of 100.3 C and molal boiling point elevation constant, kb=0.87 C*kg*mol. Calculate the boiling point of a solution made of 26.96 g of urea (NH2)2CO) dissolved in 550 g of X.
43.4 g/dL x (10 mL/dL) = ? g/mL then that times 25.0 mL = ? g
delta T = Kb*molality
m = mols/kg solvent and
mols = grams/molar mass. Solver for mols, then solver for m, then for delta T.
Add delta T to 100.3 = boiling point of new solution
Post your work if you get stuck.
Sure! Let's break down each question step by step.
Question 1:
To calculate the mass of iron (II) bromide (FeBr2) added to the flask, we need to use the concentration and volume given.
1. First, convert the given concentration from grams per deciliter (g/dL) to grams per milliliter (g/mL). Since 1 mL is equal to 1/10th of a deciliter, you can divide the given concentration (43.4 g/dL) by 10, which is 4.34 g/mL.
2. Multiply the volume (25.0 mL) by the concentration (4.34 g/mL) to calculate the mass of iron (II) bromide added to the flask:
Mass = Volume x Concentration
Mass = 25.0 mL x 4.34 g/mL = 108.5 grams
Therefore, the chemist has added 108.5 grams of iron (II) bromide to the flask.
Question 2:
To calculate the boiling point of the solution, we need to use the molal boiling point elevation constant (kb), the molality of the solution, and the boiling point of the pure solvent.
1. Calculate the molality (m) of the solution using the formula:
Molality (m) = moles of solute / mass of solvent (in kg)
First, convert the given mass of urea (26.96 g) to moles by dividing it by the molar mass of urea (60.06 g/mol):
Moles of urea = 26.96 g / 60.06 g/mol = 0.4487 mol
Then, calculate the mass of the solvent (X) in kg by dividing the given mass (550 g) by 1000:
Mass of X (solvent) = 550 g / 1000 = 0.550 kg
Now, calculate the molality of the solution:
Molality (m) = 0.4487 mol / 0.550 kg = 0.8169 mol/kg
2. Use the equation for boiling point elevation to calculate the change in boiling point (ΔTb):
ΔTb = kb * m
Given that kb (molal boiling point elevation constant) is 0.87 C*kg*mol and the molality (m) is 0.8169 mol/kg:
ΔTb = 0.87 C*kg*mol * 0.8169 mol/kg = 0.7106 C
3. Finally, add the change in boiling point (ΔTb) to the normal boiling point of the pure solvent (100.3 C):
Boiling point of solution = 100.3 C + 0.7106 C = 101.01 C
Therefore, the boiling point of the solution made of 26.96 g of urea dissolved in 550 g of X is approximately 101.01 C.