Tuyển tập 25 đề thi học sinh giỏi Hóa học lớp 9 (kèm đáp án) (by Dameva)
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TUYỂN TẬP 50 ĐỀ THI HỌC SINH GIỎI MÔN HÓA HỌC LỚP 9 (<strong>kèm</strong> <strong>đáp</strong> <strong>án</strong>)<br />
C©u 2.1<br />
1.5<br />
®iÓm<br />
C©u 2.2<br />
1.5<br />
®iÓm<br />
C©u 3<br />
2.0<br />
c« c¹n phÇn dung dÞch thu ®−îc FeCl 2 .<br />
PhÇn n−íc läc gåm NaAlO 2 vµ NaOH d− ®−îc xö lÝ b»ng CO 2 d− ( hoÆc H +<br />
võa ®ñ)<br />
NaOH + CO 2 NaHCO 3<br />
NaAlO 2 + CO 2 + 2H 2 O NaHCO 3 + Al(OH) 3 <br />
Läc lÊy Al(OH) 3 kÕt tña cho t¸c dông víi HCl d− :<br />
Al(OH) 3 + 3HCl AlCl 3 + 3H 2 O<br />
C« c¹n dung dÞch thu ®−îc AlCl 3 .<br />
Kh«ng khÝ l<strong>án</strong>g ®em ch−ng ph©n biÖt ®−îc N 2 vµ O 2 <br />
§iÖn ph©n n−íc: 2H 2 O<br />
⎯⎯→<br />
dp<br />
Tæng hîp amoniac: N 2 + 3H 2<br />
2H 2 + O 2 <br />
⎯ t ⎯ o , Pt →<br />
4NH 3 + 5O 2 ⎯ t ⎯ o , Pt → 4NO + 6H 2 O<br />
2NO + O 2 2NO 2<br />
4NO 2 + O 2 +2H 2 O 4HNO 3<br />
NH 3 + HNO 3 NH 4 NO 3 (®¹m 2 l¸)<br />
t<br />
CaCO 3 ⎯⎯→<br />
o<br />
CaO + CO 2<br />
CO 2 + 2NH 3 (NH 2 ) 2 CO + H 2 O<br />
( Urª)<br />
2NH 3<br />
1<br />
Na + H 2 O NaOH + H2 (1)<br />
2<br />
2a a mol<br />
CO 2 + 2NaOH Na 2 CO 3 + H 2 O (2)<br />
b 2b mol<br />
khi 2b = 2a a = b dd Y cã Na 2 CO 3 .<br />
CO 2 + NaOH NaHCO 3 (3)<br />
b 2a mol<br />
khi 2a = b Y cã NaHCO 3<br />
VËy: b 2a<br />
Na 2 CO 3 a < b < 2a NaHCO 3<br />
b < a : dd Y cã Na 2 CO 3 vµ NaOH d−<br />
b = a : dd Y cã Na 2 CO 3<br />
a < b < 2a :dd Y cã Na 2 CO 3 + NaHCO 3<br />
b ≥ 2a : dd Y cã NaHCO 3<br />
Ph−¬ng tr×nh ho¸ häc:<br />
Al 2 O 3 + 6HCl 2AlCl 3 + 3H 2 O (1)<br />
Fe 2 O 3 + 6HCl 2FeCl 3 + 3H 2 O (2)<br />
CuO + 2HCl CuCl 2 + H 2 O (3)<br />
Fe 2 O 3 + 3H 2 2Fe + 3H 2 O (4)<br />
CuO + H 2 Cu + H 2 O (5)<br />
Gäi sè mol Al 2 O 3 , Fe 2 O 3 , CuO trong thÝ nghiÖm lÇn 1 lµ x, y, z (mol).<br />
Tõ (1), (2), (3) , sè mol HCl tham gia phn øng lµ 6x, 6y, 2z.<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.5<br />
0.<strong>25</strong><br />
0.<strong>25</strong><br />
0.<strong>25</strong><br />
0.<strong>25</strong><br />
0.<strong>25</strong><br />
0.<strong>25</strong><br />
56
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