Percent by mass concentration

In summary, the conversation discusses the calculation of the mass concentration of CaCl2 in an aqueous solution using Raoult's law. The solution has a vapor pressure of 80.8mmHG at 50 degrees C, and the vapor pressure of pure water at this temperature is 92.6 mmHG. The formula used is % by mass = mass solute/mass solution, and CaCl2 is dissociated. The solution also involves using molecular weights to solve for the total mass of the solution.
  • #1
blueskadoo42
26
0
% by mass concentration

Homework Statement



An aqueous CaCL2 solution has a vapor pressure of 80.8mmHG at 50 degree C . The vapor pressure of pure water at this temperature is 92.6 mmHG .

What is the concentration of CaCl2 in mass percent?

Homework Equations



% by mass = mass solute/mass solution.

The Attempt at a Solution



I tried converting the pressure into moles then dividing the moles of CaCl2 by the total moles. I am pretty stuck..

Thanks
Skadoo!
 
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  • #2


Do you know Raoult's law?
 
  • #3


yeah i do. p = pa*xa+pb*xb correct? not sure how to solve for the x's...
 
  • #4


xa+xb=1
 
  • #5


alright knowing this, i use 'a' as the vap press for cacl2 and 'b' for vap press of water? then use molecular weights to to solve for total mass of solution..?
 
  • #6


Sounds OK. Don't forget CaCl2 is dissociated.
 
  • #7


ah right, almost forgot. Ill give this a run thanks.
 

What is percent by mass concentration?

Percent by mass concentration is a measure of the amount of a substance present in a solution or mixture, expressed as a percentage of the total mass of the solution or mixture.

How is percent by mass concentration calculated?

Percent by mass concentration is calculated by dividing the mass of the solute (substance being dissolved) by the mass of the solution or mixture, and then multiplying by 100. The formula is: % by mass = (mass of solute ÷ mass of solution) x 100%

What units are used for percent by mass concentration?

Percent by mass concentration is typically expressed in grams per 100 grams (g/100g) or in parts per hundred (pph). However, it can also be expressed in other units such as milligrams per liter (mg/L) or kilograms per cubic meter (kg/m^3).

How is percent by mass concentration different from other concentration measures?

Percent by mass concentration is different from other concentration measures, such as molarity and molality, because it takes into account the total mass of the solution rather than just the volume. This makes it a more accurate measure for solutions with varying densities.

Why is percent by mass concentration important in science?

Percent by mass concentration is important in science because it allows scientists to accurately measure the amount of a substance in a solution or mixture, which is crucial for experiments and industrial processes. It also helps with calculating the proper amount of a substance to use for a specific purpose.

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