20點 請問大學普通化學第十五章溶液的問題 急~~~

91-1-6.Calculate the molarity of solution when 5.42g Na2C2O4 (FW=134.0) is added to 250mL volumetric flask and distilled water is added until the mark is reached. (6) Calculate the concentration in terms of weight percent if the density of the solution is 1.03g/mL. (7)

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91-1-1717.What concentration of NaCl in water is needed to produce an aqueous solution isotonic with blood (=7.70atm at 25℃)? (18)

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91-1-18How many seconds must a current of 5.00A be applied to a solution of Cu2+ to produce 10.5g cupper metal? (Cu:63.55)

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91-1-22A solution was prepared by dissolving 18.00g nonelectrolyte nonvolatile compound in 150.0g water. The resulting solution has a boiling point of 100.34℃. Calculate the molar mass of the compound (Kb for water is 0.51℃kg/mol).

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92-10.A student weighs out 0.568 g of KHP (molar mass = 204 g/mol) and titrates to the equivalence point with 36.78 mL of a stock NaOH solution. What is the concentration of the stock NaOH solution? KHP is an acid with one acidic proton.

A)0.102 M B) 0.315 M C) 0.943 M D) 0.0757 M

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19. When a 20.0-g sample of an unknown compound is dissolved in 500. g of benzene, the freezing point of the resulting solution of 3.77℃.The freezing point of pure benzene is 5.48℃ and Kf for benzene is 5.12℃/m. Calculate the molar mass of the unknown compound.

A 140. B120. C100. D80.0 g/mol

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26. The decomposition of nitromethane in basic solution was studied at constant temperature. The rate law is first order in [nitromethane]. For a standard solution of 0.0100 M nitromethane, the concentration of nitromethane after 5.00 s was found to be 2.24×10-4 M.

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When a unknown sample of nitromethane was analyzed, the concentration remaining after 5.00 s was found to be 1.35×10-4 M. What is the initial concentration of nitromethane in the sample? (A) 0.00854 M (B) 0.00603 M (C) 0.00991 M (D) 0.000329 M

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10. Which of the following liquids would make a good solvent for iodine, I2?

(A) HCl (B) H2O (C) CS2 (D) CH3OH

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1. A titration was performed to find the concentration of hydrochloric acid with the following results:

TrialMolarity (M)

10.125

20.126

30.124

The actual concentration of HCl was determined to be 0.100 M; the results of the titration are:

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(A)both accurate and precise. (B)accurate but imprecise.(C)precise but inaccurate.(D)both inaccurate and imprecise.

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47. A solution of hydrogen peroxide is 30.0% H2O2 by mass and has a density of 1.11 g/cm3. The molarity of the solution is:

(A)7.94 M(B)8.82 M(C)9.79 M(D)0.980 M

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38. The following reaction occurs in basic solution:

F2 + H2O → O2 + F–

When the equation is balanced, the sum of the coefficients is:

(A)10(B)11(C)12(D)13

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37. Which of the following will not produce a buffered solution?

(A)100 mL of 0.1 M Na2CO3 and 50 mL of 0.1 M HCl(B)100 mL of 0.1 M NaHCO3 and 25 mL of 0.2 M HCl

(C)100 mL of 0.1 M Na2CO3 and 75 mL of 0.2 M HCl(D)100 mL of 0.1 M Na2CO3 and 50 mL of 0.1 M NaOH

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19. Thyroxine, an important hormone that controls the rate of metabolism in the body, can be isolated from the thyroid gland. If 0.455 g of

thyroxine is dissolved in 10.0 g of benzene, the freezing point of the solution is 5.144℃.

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Pure benzene freezes at 5.444℃ and has a value for

the molal freezing point depression constant of Kf of 5.12℃/m. What is the molar mass of thyroxine?

(A)9980 g/mol (B)777 g/mol (C)2330 g/mol (D)285 g/mol

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17. When the equation is balanced using the smallest whole-number coefficient of is

(A) 2 (B) 4 (C) 6 (D) 8 (E) 10

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25. If 45.5 g of BaCl2 are dissolved in water to produce 2.74L of solution, what is the molarity of the solution?

A) 0.219 B) 0.599 C) 0.263 D) 0.0797

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. Calculate the molality of C2H5OH in a water solution that is prepared by mixing 50.0 mL of C2H5OH with 50.0 mL of H2O at 20℃. The density of the C2H5OH is 0.789 g/mL at 20℃.

(A) 17.2 m (B) 4.28 m (C) 1.24 m (D) 8.56 m

1 個解答

• Lv 5
9 年前
最佳解答

把題目打上來還比較有誠意ㄧ點，這樣沒有人會想要幫你解答= =

PS 我根本找不到怎麼去那些問題

2012-04-17 19:30:16 補充：

晚上才看到你發這篇...

如果還需要解答，我可以寫給你，但不知道你還需不需要。

需要請來個通知

2012-04-21 22:03:56 補充：

1. 假設van Hoff factor = 1

那滲透壓=7.70 atm = CRT, R = 0.08206

C = 0.315 M = [NaCl]

兩種離子: 0.315/2 = 0.157 M

2. Cu2+ + 2e -> Cu

10.5 g/63.55 = 0.33 mol

0.33 mol *F (96485 C/mol) = 31883.32 C

I = C/t, so t = C/I = 31883.32/5 = 6377 s

3. t = 0, 0.01 M; t = 5, 2.24E-4

[N]/[N]0 = 2.24E-4/0.01 = 0.0224 = EXP(-5k)

k = 0.76 /s

For unknown, 1.35E-4 = [N]0 * EXP(-0.76*5)

[N]0 = 0.006 M

4. C, precise but inaccurate: inaccuracy is the systematic error, precision is random error.

5. D, balanced: 2 H2O + 2F2 -> O2 + 4H+ + 4F- (13)

6. C, strong acid must be less in mole than buffering solution

7. B, 777 g/mol

dT = Kf * Cm (molality, mol/kg)

Kf = 5.12 (你的單位怪怪的就是了), dT = 5.444-5.144 = 0.3

Cm = 0.0586 mol/kg

10g benzene, so 5.86E-4 mol of thyroxine.

No. gram = 0.455 g, so 0.455/0.000586 = 777 g/mol

8. A; molality = mole of solute / mass of solvent (not solution)

所以 50 mL * 0.789 g/mL = 39.45 g, -> 39.45/(24+5+17) = 0.858 mol of ethanol.

50mL of water, (assume density = 1.0), = 50 g = 0.05 kg.

所以 0.858mol/0.05kg = 17.2 mol/kg

參考資料： myself