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Salty Bubbles Presentation by Sana Panjwani & Alice Yang.

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Presentation on theme: "Salty Bubbles Presentation by Sana Panjwani & Alice Yang."— Presentation transcript:

1 Salty Bubbles Presentation by Sana Panjwani & Alice Yang

2 2 Purpose To determine the influence of the amount of solute on the boiling point

3 3 Our materials We tested 3 different amounts of NaCl:  15 g  30 g  43g We kept a constant of 50 mL H 2 O each trial

4 4 Time for Notes

5 5 Key Terms #2a solute: the substance that will be dissolved. Ex: NaCl(s) #2b solvent: substance that will do the dissolving. Ex: H 2 O(l)

6 6 #4 Polar dissolve other polars  Ex: H 2 O and NaCl Nonpolar dissolves other nonpolars  Motor oil and gasoline

7 7 #15a Dissociation- separation of ions that occurs when an ionic compound dissolves NaCl(s) H2O Na + (aq)+ Cl - (aq)

8 8 #10 Electrolyte- any substance that dissociates into ions when dissolved in a suitable medium or melted. forms a conductor of electricity. NaCl is a strong electrolyte, meaning that most of its bonds will break to form ions. As opposed to a weak electrolyte and its few bonds that break into ions.

9 9 #12 molality (m): number of mole of solute amount of solvent (kg) NOT the same as #2d or #11 molarity (M) M= m= the mass of the solute will not change with varying temperatures, while the volume of the solvent will. Therefore, for our experiment, molality would provide a constant mass to work with. Number of moles of solute Amount of solvent (L) Number of mole of solute Amount of solvent (kg)

10 10 #16 Colligative properties- any property of a solution that is changed by the addition of a solute. Ex: adding NaCl to water increases the boiling point.

11 11 #17b dealing with colligative properties:  Electrolytes in solutions. As stated before, NaCl, an electrolyte, increases boiling point when it is added to water. How to see this mathematically requires the use of a formula.

12 12 Δt = mK b ( ) Δ delta (change) t temperature m molality K b constant. For water, it is.51 C/m Moles of ions Per electrolyte in solution

13 13 Δt = Δt: we are solving for the change in temp. to see if increasing amounts of NaCl will increase the boiling point. Our first amount of NaCl that we tested was 15g

14 14 m molality: number of mole of solute amount of solvent (kg) Step 1: find number of mole of solute. Use dimensional analysis 15 g NaCl 1 mol NaCl g NaCl.257 mol NaCl

15 15 m cont. Step 2: find amount of solvent (kg) * remember that 1 mL of water = 1 g of water 50 mL H 2 O = 50 g H 2 O =.050 kg H 2 O Step 3: plug back in to find m. 257 mol NaCl.050 kg H 2 O mol/kg m

16 16 KbKb K b of water is.51 C/m

17 17 How many moles of ions are there for every electrolyte? (think back to dissociation) NaCl(s) From 1 mol NaCl(s), the reaction yields 1 mol Na (aq) and 1 mol Cl (aq). So for every electrolyte in the solution, you have 2 mols of ions. Moles of ions Per electrolyte in solution H2OH2O Na + (aq)+ Cl - (aq)

18 18 Plugging the numbers in. Δt = mK b ( ) Δt= (5.140)(.51)(2) Δt= we should find that the boiling point of the solution increases by about 5°C when 15 g NaCl is added Moles of ions Per electrolyte in solution

19 19 Your Turn! Attempt to find the change in temperature for an added 30 g NaCl.

20 20 Your turn! Remember the formulas: Δt = mK b ( ) m= K b =.51 C/m Moles of ions Per electrolyte in solution Number of moles of solute Amount of solvent (kg) moles of ions Per electrolyte in solution 2

21 21 30 g NaCl 1 mol NaCl g NaCl K b =.51 C/m 2 moles of ions Per electrolyte in solution mol/kg.513 mol NaCl.050 kg H 2 O

22 22 Δt = mK b () Δt = (10.266) (.51) (2) Δt = The new boiling point temperature should increase by about 10ºC. Moles of ions Per electrolyte in solution

23 23 With 43g NaCl Δt = mK b ( ) Moles of ions Per electrolyte in solution Δt = (14.715)(.51)(2) Δt =15.009

24 24 Conclusion An increased amount of NaCl solute in the tap water will result in an increase in the boiling point of the solution.


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