Chemistry

posted by .

Explain the following observations using chem principles:

When table salt and sugar are dissolved in water, it is observed that:

1. Both solutions have a higher boiling point than pure water.

2. the boiling point of .1 M NaCl solution is higher than that of .1 M C12H22O11 solution.

---------------------------------------
1. I was thinking the salt and the sucrose have a higher vapor pressure which causes the vapor pressure of the solution to increase and decrease the volatility.

2. not sure about number 2

  • Chemistry -

    Consider on number 2 that NaCl breaks into two particles when dissoved, which doubles the effect on colligative properties.

  • Chemistry -

    1 is in the right ball park but the wrong direction.
    For #1, both salt and sugar lower the vapor pressure of the solution compared to that of pure water. Lowering the vapor pressure of water means that it must be raised to a higher temperature before it reaches 1 atmosphere vapor presure (which is the definition of boiling point for a liquid).
    2. The increase in boiling point, the decrease in freezing point, and the change in vapor pressure when a non-volatile solute is dissolved in a volatile solvent, depends solely upon the number of dissolved particles. Mole for mole, sucrose has 1 particle per molecule while NaCl has two particles per molecule. Therefore, a 0.1 M NaCl will increase the boiling point of water almost twice as much as 0.1 M sucrose.

  • Chemistry -

    Ok, for number 2: NaCl breaks into 2 particles when dissolved whereas sucrose remains as one. This doubles the van't Hoff factor which means a higher temperature is required for it to vaporize.

    Does that make sense?

    Re: number one. Is that answer ok?

  • Chemistry -

    Your revised number 2 answer is great. No, your original answer to number 1 is not correct. Take another look at my resonse to your number 1.

  • Chemistry -

    I hadn't even seen your response DrBob. Thanks! Making more sense to me now.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    1. Which of the following is not true? a. The freezing point of sea water is lower than the freezing point of pure water. b. The boiling point of a water sample from the Salt Lake is lower than the boiling point of pure water. c. The
  2. science

    When substances such as sugar and table salt are dissolved in water, the freezing points of the new solutions are lower than the freezing point of water. Also, the more material dissolved, the lower the freezing point. The boiling …
  3. science

    When substances such as sugar and table salt are dissolved in water, the freezing points of the new solutions are lower than the freezing point of water. Also, the more material dissolved, the lower the freezing point. The boiling …
  4. science

    When substances such as sugar and table salt are dissolved in water, the freezing points of the new solutions are lower than the freezing point of water. Also, the more material dissolved, the lower the freezing point. The boiling …
  5. Chemistry

    Which of the following statements about boiling points are false: A. the boiling point of 0.1 m KF(aq) is lower than the boiling point of 0.1 m ethanol(aq) B. the boiling point of a 0.5 m aqueous solution of NaOH is the same as the …
  6. chemistry

    Compute the boiling point elevation of a salt water solution that contains 2.60 g of NaCl dissolved in 121 ml of water. Enter the number of degrees celsius that the boiling point will be elevated.
  7. chemistry(Please check)

    1) In comparing the phase diagram for water with that of a solution of sugar in water, all of the following decrease except a) the vapor pressure b) the boiling point c) the freezing point d) the triple point I chose the boiling point …
  8. Chemistry

    Pure water boils at 100ºC (212ºF). When a substance is added to the water the boiling point increases due to what is referred to as the boiling point elevation. (a) What is the molecular mass of sucrose (C₁₂H₂₂O₁₁)?
  9. chemistry

    Which of the following statements about boiling points are true?
  10. Science

    Which of the following solutions would have the highest boiling point?

More Similar Questions