Question

A solution is prepared by dissolving 15.0 g of nh3 in 250.0 g of water. the density of the resulting 7)solution is 0.974 g/ml. the molality of nh3 in the solution is __________.

Answer 1

0.0597 
 Mole fraction NH3 = moles NH3 / total moles in solution  
 moles NH3 = mass / molar mass  
 = 15.0 g / 17.034 g/mol  
 = 0.88059 moles    
 moles H2O = 250 g / 18.016 g/mol  
 = 13.8766 mol    
 total moles = 0.88059 + 13.8766  
 = 14.757 mol    
 fole fraction NH3 = 0.88059 / 14.757   
= 0.0597

Answer 2

To overcome this problem, we first assume the volume is purely additive. The density of the mixture can then be calculated by adding up the mass fraction of each component divided by the density of each:

1 / ρ mixture = (x NH3 / ρ NH3) + (x H2O / ρ H2O) ---> 1

Further Explanation

Calculate the mass fraction of NH3:

x NH3 = 15 g / (15 g + 250 g)

x NH3 = 0.0566

Therefore the water mass fraction is:

x H2O = 1 - x NH3 = 1 - 0.0566

x H2O = 0.9434

Assuming that the density of water is 1 g / mL and replaces known values ​​back to equation 1:

1 / 0.974 g / mL = [0.0566 / (ρ NH3)] + [0.9434 / (1 g / mL)]

NH3 = 0.680 g / mL

Given the density of NH3, we can now calculate the volume of NH3:

V NH3 = 15 g / 0.680 g / mL

V NH3 = 22.07 mL

The number of moles of NH3 are: (molar mass of NH3 is 17.03 g / mol)

n NH3 = 15 g / 17.03 g / mol

n NH3 = 0.881 mol

Therefore the NH3 molarity in solution is:

Molarity = 0.881 mol / [(22.07 mL + 250 mL) * (1L / 1000 mL)

M = 3.238 mol / L = 3.24 M

Learn More

Molarity  brainly.com/question/7548948

Mass Fraction  brainly.com/question/7548948

Details

Grade: High School

Subject: Chemistry

Keyword: Molarity, Mass, fraction