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Kit Kit asked in 科學及數學化學 · 10 years ago

Chem問題幾條 極度急plz!!! 20分

1. The number of outermost shell electrons of four elements are listed in the table below:

Element W : 4 outermost shell electrons in the atom

Element X : 5 outermost shell electrons in the atom

Element Y : 6 outermost shell electrons in the atom

Element Z : 7 outermost shell electrons in the atom

PS: W,X,Y,Z are not chemical symbols

a.). Give the formula of the molecule formed from W and Y.

b.). With the aid of electron diagram, predict and explain the shape of molecule from W and Y.

c.With the help of a suitable diagram, state and explain which two elements can form a molecule that like a trigonal pyramidal.

2. Sulphur and fluorine can form various kinds of molecules such as SF2 and SF6.A larger 'SF' molecule is known as S2F10.

a.).Give the bond angles in SF2 and SF6.

b.). State whether SF2 and SF6 are polar and non-polar.

c.). S2F10 is similar to SF6 as they have the same bond angle.(Draw the 3D representation.(Bonus)

d.). Is S2F10 a polar or non-polar molecule? Explain your answer.

3. The solubility of iodine in tetrachloromethane at 10 degreeC is 3g per 100cm3. The solubility of iodine in water at 10degreeC is 0.02g per 100 cm3. A solution of iodine in tetrachloromethane is violet while an aqueous solution of iodine is yellow.

a.).(1) State whether: Iodine molecules is polar or non-polar.

(2) Tetrachloromethane molecule is polar or non-polar.

(3) Water molecule is polar / non-polar

b.). Hence, explain why iodine is much more soluble in tetrachloromethane than in water.

c.). Predict whether tetrachloromethane dissolves in water or not.

d.). Describe what happens when an aqueous iodine solution is shaken with an equal volume of tetrachloromethane.

Update:

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1 Answer

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  • 10 years ago
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    1a) WY2

    b)

    圖片參考:http://i453.photobucket.com/albums/qq252/tomchan12...

    With no lone pairs and two bond pairs in central atom W, it has a linear shape.

    c) WZ3, with one lone pair and three bond pairs in central atom W, it has a trigonal pyramidal shape. (You draw the 3-D diagram by yourself)

    2.a) SF2: about 105 deg

    SF6: 90 deg

    b) SF2 is a polar molecule because the molecules are arranged in asymmetrical manner so that the dipole moments of S-F bonds cannot cancel out each other. There is a net dipole moment to make the SF2 molecules polar.

    SF6 is a non-polar molecule because the molecules are arranged in symmetrical manner so that the dipole moments of S-F bonds can cancel out each other. The net dipole moment of SF6 is zero to make it non-polar.

    c)

    圖片參考:http://i453.photobucket.com/albums/qq252/tomchan12...

    d) Just a guess: It is a non-polar molecule. S2F10 molecules are similar to SF6 molecules that are also arranged symmetrically with the dipole moments of S-F bonds cancel out each other. The net dipole moment is hence equal to zero. So it should be a non-polar molecule.

    3a)(i) non-polar

    (ii) non-polar

    (iii) polar

    (b) According to the principle 'like dissolve like', both iodine and tetrachloromethane is non-polar in nature. So iodine is soluble in tetrachloromethane and less likely to be soluble in polar water molecules.

    c) No

    d) A yellow layer at the top and a violet layer at the bottom in test tube should be observed. Since tetrachloromethane is a non-aqueous organic solvent. It extracts most iodine from the aqueous layer. So iodine will give a violet colour in organic solvent.

    2011-10-10 21:31:00 補充:

    Typo:

    1c) should be XZ3.

    Source(s): Knowledge is power.
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