What is the molality of a solution containing 11.6 g of urea nh2 2co in a 865.2 grams of water

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Number four

Step by step solution

Molality can be calculated by the following formula.

From the given,

Mass of urea = 7.78 g

Let’s convert the mass of urea into moles.

Molar mass of urea = 60.055 g/mol

Let’s calculate the moles of urea.

Hence, moles of urea are 0.1295.

"Molarity= moles\/litre"

Moles = 7.78/60 =0.1297moles

Molarity= (0.1297× 0.203)/1000

= 2.63×10-3M

Number five

Moles of Lead =2.67moles

Number six

a) 35 mL (0.790 g/mL) = 27.65 g acetone

50 mL (0.789 g/mL) = 39.45 g ethyl alcohol

total = 67.1 g

( 27.65 / 67.1 )100

= 41.2 mass% acetone

b)the volume percent of ethyl alcohol in the solution

(50 / 85 )100

= 58.8 vol% ethyl alcohol

c)Convert grams from part a into moles acetone and moles EtOH.

Sum moles to get a total moles.

Then

mole fraction acetone

= (moles acetone/total moles)

=Mole fraction of ethyl alcohol = moles of ethyl alcohol/total moles

Mole fraction of acetone=0.46

Question: How many grams of sodium chloride per kilogram of water are present in a 2.7 m aqueous solution?

1. Write the equation for calculating molality:

   molality = moles(solute) ÷ mass(solvent in kg)

2. Rearrange equation to find moles(solute):

   molality

   =

   moles(solute)   mass(solvent in kg)

   
   

   molality × mass(solvent in kg)

   =

   moles(solute) ×   mass(solvent) mass(solvent)

   
   

   moles(solute)

   =

   molality × mass(solvent in kg)

3. Identify the solute and solvent that make up the solution:

   solute = sodium chloride = NaCl
   solvent = water

4. Calculate moles of solute :

   moles(solute) = molality × mass(solvent in kg)
   molality = 2.7 m mass(solvent in kg) = 1 kg

   moles(NaCl) = 2.7 × 1 = 2.7 mol

5. Calculate mass of solute :

   moles(solute) = mass(solute in g) ÷ molar mass(solute in g mol-1) Rearrange equation to find mass:

   mass(solute) = moles(solute) × molar mass

   moles(NaCl) = 2.7 mol

   molar mass(NaCl) = 22.99 + 35.45 = 58.44 g mol-1

   
   mass(NaCl) = 2.7 × 58.44 = 157.79 g