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Salty Bubbles

Salty Bubbles. Presentation by Sana Panjwani & Alice Yang. Purpose. To determine the influence of the amount of solute on the boiling point. 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. Time for Notes. Key Terms.

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Salty Bubbles

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  1. Salty Bubbles Presentation by Sana Panjwani & Alice Yang

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

  3. Our materials • We tested 3 different amounts of NaCl: • 15 g • 30 g • 43g • We kept a constant of 50 mL H2O each trial

  4. Time for Notes

  5. Key Terms • #2a solute: the substance that will be dissolved. Ex: NaCl(s) • #2b solvent: substance that will do the dissolving. Ex: H2O(l)

  6. #4 • Polar dissolve other polars • Ex: H2O and NaCl • Nonpolar dissolves other nonpolars • Motor oil and gasoline

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

  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. #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 mole of solute Number of moles of solute Amount of solvent (kg) Amount of solvent (L)

  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. #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. Δt = mKb( ) Moles of ions Per electrolyte in solution • Δ delta (change) • t temperature • m molality • Kb constant. For water, it is .51 C/m

  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. 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 58.443 g NaCl .257 mol NaCl

  15. m cont. • Step 2: find amount of solvent (kg) * remember that 1 mL of water = 1 g of water 50 mL H2O = 50 g H2O = .050 kg H2O • Step 3: plug back in to find m .257 mol NaCl .050 kg H2O 5.140 mol/kg m

  16. Kb • Kb of water is.51 C/m

  17. Moles of ions Per electrolyte in solution • 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. H2O Na+ (aq) + Cl- (aq)

  18. Plugging the numbers in. • Δt = mKb( ) • Δt= (5.140)(.51)(2) • Δt= 5.243 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. Your Turn! Attempt to find the change in temperature for an added 30 g NaCl.

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

  21. .513 mol NaCl 30 g NaCl 1 mol NaCl 58.443 g NaCl Kb= .51 C/m 2 .513 mol NaCl 10.260 mol/kg .050 kg H2O moles of ions Per electrolyte in solution

  22. Moles of ions Per electrolyte in solution • Δt = mKb ( ) • Δt = (10.266) (.51) (2) • Δt = 10.471 • The new boiling point temperature should increase by about 10ºC.

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

  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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