匿名使用者
匿名使用者 發問時間: 科學化學 · 9 年前

20點 請問大學普通化學第十五章溶液的問題 急~~~

請大家盡快幫我解答以下的化學問題

盡快星期二中午前 ,謝謝大家。

以下的題目是從轉學考中找的

請上http://www.ncyu.edu.tw/academic/gradation.aspx?sit... 看題目

以下僅列出年度及題號 年-題號93-35,91-1-6,94-1,94-47,96-25,93-26,91-1-17,93-10,91-1-18,91-1-22,92-10,92-19,94-19,94-37,94-38,95-17,100-31

上面像是91-1-17 (中間多一個1的)我也不知道是什麼意思 因為題目是同學找給我的 不過看題目好像沒差 你就把中間的1當沒有吧!

已更新項目:

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)

2 個已更新項目:

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

3 個已更新項目:

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)

4 個已更新項目:

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).

5 個已更新項目:

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

6 個已更新項目:

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

7 個已更新項目:

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.

8 個已更新項目:

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

9 個已更新項目:

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

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

10 個已更新項目:

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:

11 個已更新項目:

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

12 個已更新項目:

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

13 個已更新項目:

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

14 個已更新項目:

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

15 個已更新項目:

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℃.

16 個已更新項目:

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

17 個已更新項目:

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

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

18 個已更新項目:

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

19 個已更新項目:

. 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

評分
  • 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
還有問題?馬上發問,尋求解答。