29.10. S6' amin thofm bac m6t ling vdi c6ng thiic phan tir C7HyN la Ạ 3. B. 5. C. 2. D.4. P H A N I I H U d N G D A N C H O N D A P A N B A I T H l T R A C N G H I E M T H E O C A U T R U C D E T H l A . M O T S O P H L / O N G P H A P G I A I N H A N H C A C B A I T O A N T R A C N G H I E M H O A H O C
I . PHl/ONG PHAP BAO T O A N K H O I L l / O N G
Ap dung djnh luat bao toan kh6'i lugng (BTKL) cho cac qua trinh bien d6i hoa hoc, ta c6:
Tcfng khoi hmig car chat tham gia phan Aug bang long khoi lifcrng cac 'n phd'm.
Máu chd't quan trong cua phirong phap nay la tim m6'i lien he giua s6' ol cac chat trong phan ling. Dua vao dinh luat nay c6 thé giai m6t each
don gian va nhanh chong nhieu bai toan hoa hoc phiic tap, dac biet a nhirng
bai toan h6n hop nhiSu chat.
Thi du 1. Hoa tan 10 gam h6n hop hai mu6'i cacbonat ciia hai kim loai
hoa tri I I va I I I bang dung djch axit HCl du, thu dugc dung dich A va 0,672 lit khi bay ra (dktc).
Kh6'i lirgng mu6'i khan thu dugc khi c6 can dung dich A la Ạ 10,33 gam. B. 33,10 gam. C. 11,82 gam. D. 9,86 gam.
Hu&ng dan gidi: Dap an dung la Ạ
Ggi X la kim loai hoa tn I I , Y la kim loai hoa trj I I I . Cac phuong trinh hoa hoc:
XCO, + 2HC1 ^ XCl, + C O j t + H2O (1)
Y^iCO,)^ + 6HC1 2YC1, + 3 C 0 2 t + 3H2O (2)
Theo (1) va (2): n„,^ - n,,^,,; n^^., = 2nt,,^.
n = M Z 2 =o,03(mol)
22,4
Theo dinh luat BTKL, ta c6:
'^(xa,>YCi,) ~ ^ x c o , "^Yjcco,), + " l n r i " ^ T l a ) , " " " ^ l U )
= 10 + 36,5.0,06-0,03.44-0,03.18 = 10,33 gam => Dap an Ạ
Thi du 2. Hoa tan hoan toan 3,22 gam h6n hop X g6m Fe, Mg va Zn
bang m6t lugng vira du dung dich H2SO4 loang, thu dugc 1,344 lit H2 (dktc) va dung djch chiJa m gam mu6'ị va dung djch chiJa m gam mu6'ị
Gia tri cua m la
Ạ 9,52. B. 10,27.
C. 8,98. D.7,25.
Hu&ng đn gidi: Dap an diing la C.
So d6 bién đi:
X (Fe, Mg, Zn) > mu6'i + Hjt
1 344
Theo sg do: S6' mol H.SỌ = s6' mol H, = = 0,06 (mol). ' 22,4 ' 22,4