21)Which aqueous solution has the highest boiling point? 31,5 M CaCl2 (aq) B, 2.

Question

21)Which aqueous solution has the highest boiling point? 31,5 M CaCl2 (aq) B, 2.0 M GH1206 (sugar) (aa) C. 2.0 M NaBr (aq)D. 2.0 M KNOs (aa) covalent bond occurs between: A. a metal with high ionization energy and an element with high electron affinity B. an element with low ionization energy and an element with low electron affinity. an element with high ionization energy and an element with high eiectron affinity D. a metal with low ionization energy and an element with low electron affinity 23) At 25 °C, water (H2O) has a vapo r pressure of 24 torr, ethanol (C2HsO) has a vapor pressure of 3 torr, and hexane (CsH14) has a vapor pressure of 150 torr. Which of the following statements about these three liquids is correct? A. Water has the lowest boiling point Hexane has the least intermolecular hydrogen bonding C. Hexane has the greatest surface tension D. Ethanol has the greatest heat of vaporization 24 What is the percent yield of the reaction below if 3.18 g of Cas(PO.)2 are produced from 24.6 m 1.55 M CaCl2 aqueous solution and an excess of sodium phosphate in aqueous solution? 3 CaCl2 (aq) + 2 Na3PO4 (aq) 6 NaCl (aq) + Ca3(PO4)2 (s) Molar masses: CaC2 -111.1 g/mol: Cas(PO4)2 -310.3 g/mol A. 92% (B) 81% C. 75% D. 65%

Explanation / Answer

21. Boiling point elevation depend upon the concentration of solute present. Aqueous solution of a nonvolatile molecular solute does not break up or ionize at all when it dissolves, such as glucose will have very less increase in boiling point.

CaCl2 ionizes to produce 3 ions (CaCl2 ---> Ca2+ + 2Cl-). If 1.5 mol of CaCl2 dissolves the concentration of ions will be 4.5 mol.

NaBr ionizes to produce 2 ions (NaBr ---> Na+ + Br-). If 2 mol of NaBr dissolves the concentration of ions will be 4 mol.

KNO3 ionizes to produce 2 ions (KNO3 --> K+ + NO3-   ). If 2 mol of KNO3 dissolves the concentration of ions will be 4 mol.

Since the CaC2 produces the greatest concentration of solute particles, it will raise the boiling point of the water to the greatest extent. Thus the answer is A.

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