尼尼 發問時間: 科學化學 · 1 0 年前

化學題目尋求答案

Compound X2Y is 60% X by mass. Calculate the percent Y by mass of the compound X2Y2.

A)20%

B)30%

C)40%

D)60%

E)80%

答案是A嗎

Which pair of ions would not be expected to from a precipitate when dilute solutions of each are mixed?

A)cu2+ s2-

B)ag+ cl-

C)ca2+ po4 3-

D)mn2+ oh-

E)mg2+ so4 2-

4 個解答

評分
  • 御風
    Lv 4
    1 0 年前
    最佳解答

    我先說聲抱歉,我從以前到現在沒用過英文回答化學問題耶...這應該是大學才用的吧?所以我就用中文回答唷^^*

    Compound X2Y is 60% X by mass. Calculate the percent Y by mass of the compound X2Y2.

    A)20%

    B)30%

    C)40%

    D)60%

    E)80%

    這題其實就是道爾吞的"倍比定律"的運用,

    倍比定律內容:若兩元素可以生成兩種或兩種以上的化合物時,在這些化合物中,一元素的質量固定,則另一元素的質量成簡單整數比。

    所以這題可以簡單的用一個九宮格來呈現

    X Y

    -------- --------- ------------

    X2Y 60 40 當我們把X固定時,可知Y的比例為1:2

    -------- --------- ------------ 所以所求Y的所佔的比例為80/60+80=57.1

    X2Y2 60 80 故答案應選擇 D

    Which pair of ions would not be expected to from a precipitate when dilute solutions of each are mixed?

    A)cu2+ s2-

    B)ag+ cl-

    C)ca2+ po4 3-

    D)mn2+ oh-

    E)mg2+ so4 2-

    這題需要用到離子沉澱表,所以還是需要背一下喔!!

    (A)會產生CuS沉澱 (黑色)

    (B)會產生AgCl沉澱 (白色)

    (C)會產生Ca3(PO4)2沉澱 (白色)

    (D)會產生MnO2沉澱 (綠色)

    http://mail.mcjh.kl.edu.tw/~jcchen/ware/asp.htm

    以上的網站可以點進去參考看看喔((離子沉澱表....

    2010-04-30 22:29:38 補充:

    對不起..

    九宮格打起來有點亂

    X Y

    ----- ------- --------

    X2Y 60 40

    ----- ------- --------

    X2Y2 60 80

    當我們把X固定時,可知Y的比例為1:2

    所以所求Y的所佔的比例為80/60+80=57.1

    故答案應選 D

    2010-04-30 22:36:10 補充:

    痾ˇ...

    好像還是依樣吼!!

    那我用數學的數列來說好了..

    (1,1)是空白

    (1,2)是X

    (1,3)是Y

    (2,1)是X2Y

    (2,2)是60

    (2,3)是40

    (3,1)是X2Y2

    (3,2)是60

    (3,3)是80

    參考資料: Me, Me, me
  • 小白
    Lv 7
    1 0 年前

    wanszeto是對的

  • 1 0 年前

    Compound X2Y is 60% X by mass. Calculate the percent Y by mass of the compound X2Y2.

    The answer is 57.1%.

    There is no exact answer from A to D

    The closet answer is D) 60%

    Let a g/mol and b g/mol be the molar masses of X and Y respectively.

    In X2Y, mass ratio X : Y

    2a : 1b = 60 : (100 - 60)

    2a : b = 60 : 40

    a : b = 30 : 40 = 3 : 4

    In X2Y2, mass ratio

    = 2x3 : 2x4

    = 3 : 4

    Percent Y by mass of the compound X2Y2

    = [4/(3+4)] x 100%

    = 57.1%

    Which pair of ions would not be expected to from a precipitate when dilute solutions of each are mixed?

    E) Mg2 + SO4 2-

    MgSO4 is soluble in water.

    CuS, AgCl, Ca3(PO4)2 and Mn(OH)2 are insoluble in water.

    參考資料: wanszeto
  • ?
    Lv 4
    1 0 年前

    Compound X2Y is 60% X by mass. Calculate the percent Y by mass of the compound X2Y2.

    for X2Y

    X = 0.3

    Y= 0.4

    ====================

    FOR X2Y2

    X2Y2= 0.6+0.8 = 1.4

    Y = 0.4/1.4 =0.286---------------(B)

    Which pair of ions would not be expected to from a precipitate when dilute solutions of each are mixed?

    (D)

    2010-05-01 17:51:20 補充:

    FOR X2Y2

    X2Y2= 0.6+0.8 = 1.4

    Y = 0.4/1.4 =0.286---------------(B)====> 寫錯了Y = 0.8/1.4 =0.57

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