Colligative Properties (How do solutes affect temperatures?) Model 1: Boiling an
ID: 1083330 • Letter: C
Question
Colligative Properties (How do solutes affect temperatures?) Model 1: Boiling and freezing points of selected solutions (1 L total volume) Solution Water 1.0 M Nact 2.0 M NaC 1.0 M glucose 1.0 M KBr 1.0 M CaCih 1.0 M Na2S Bolling point (°C) Freezing point (C) 100 101 102 100.5 101 101.5 101.5 0.0 -3.8 -3.8 -5.7 -5.7 Critical Thinking Questions: 1. Does the bolling point of water increase or decrease with the addition of solute? 2. Does the freezing point of water increase or decrease with the addition of solute? 3. By how much does the bolling point of 1 L of water change with the addition of one mole 2of Naci? 4. By how much does the boiling point of 1 L of water change with the addition of one mole of glucose? 5. As a team, discuss and predict a reason for the difference between the changes caused by 1.0 M NaCi and 1.0 M glucose. (Hint: The formula of glucose is CeH20s. What is the major difference?) 6. What difference, If any, is there in the effects of 1.0 M NaCI and 1.0 M KBr on the boiling point? What difference, if any, is there in the effects of 1.0 M NaCI and 1.0 M CaCh on the bolling point? 7. 8. Discuss with your team and predict a reason for the difference between the changes caused by NaCI and CaC. CA298 144-Explanation / Answer
Q1. The boiling point of water increases with the addition of a solute
Q2. The freezing point of water decreases with the addition of solute
Q3. 1 mole of something in 1 liter is 1M so the addition of 1 mole of NaCl corresponds to the value of 1 M NaCl in the chart we see the boiling point is 101 C so the boiling point of water has changed by 1 C
Q4. 1 mole of glucose corresponds to 1 M glucose boiling point of 1 M glucose is 100.5C so it has changed by 0.5C
Q5. 1 M glucose is 0.5 C and 1 M NaCl is 1 C, the double compared to that of glucose, difference is because the NaCl dissociates into 2 ions while glucose dont, so when you add 1 mole of NaCl you have 1 M for Na ions and 1 M for Cl ions
Q6. There is no difference in the effect of adding 1 mole of Kbr or NaCl they have the same boiling points (101) (Both compounds dissociates into 2 ions)
Q7 and Q8. 1 M NaCl and 1 M CaCl2 , 101 C and 101.5 C respectively difference is 0.5 C, this is the same reason as the one give in Q5, NaCl dissociates into 2 ions
CaCl2 ==== Ca+ + 2 Cl-, it dissociates into 3 ions so in 1 M Ca Cl2 you have 1 M for Ca and 2 M for Cl
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