Pb + 3H2S04(dac) — ^ Pb(HS04)2 + SO2 + 2H2O v i ^ i , •
3Pb + 8HNO3 (loang) .0 2Pb + O, 2PbO -> 3Pb(N03)2 + 2NO + 4H2O ,0 Pb + CI2 PbCU Pb + S — ^ PbS (den) 2Pb + 2H2O + O2 > 2Pb(OH)2
Pb + 2KOH + 2H2O > K2[Pb(OH)4] + H2t
Dang 1; Bai tap ve crom va hap chat ciia crom
1. Cho m gam b6t crom phan ling hoan toan vdi dung djch HCl (du), thu ducfc V lit
khi H ; (dktc). Mat khac, cung m gam bot crom trfin phan ung hoan toan vdi khi
O2 (du), thu duoc 15,2 gam oxit duy nhát. Gia tn ciia V la
kẠ 2,24 B.6,72 C. 4,48 D. 3,36 Hu&ng đn gidi Theobaira: nc^03 =15,2/152 = 0,lmol 2Cr + - 0 , 2 ^ >Cr20, 0,2 <- 0,1 (mol) Cr + 2HCl->CrCl2+H2 t 0,2 ^ 0,2 (mol) Vay: V = 0,2.22,4 = 4,48(1) i ; Dap an dung la C.
^. Co 150ml dung djch CrQ, I M tac dung vira dii m gam b6t kem. Gia tri ciia m la ^ Ạ 14,625 B. 19,500 C. 9,750 D. 4,875.
Huong đn gidi
riúin locii vii /;i>phdp gidi nhanh ET Hoa hoc 12 — Cii Thanh 1 odn
Theo bai ra: S6' mol CrCl, = 0,15.1 = 0,15 mol PTPIT: Zn + CrQ., ZnCU +2CTC\^
0,075 < - 0 , 1 5 mol
=>nz„ = 0 , 1 5 / 2 = 0,075 (mol) ^ m^, = 0,075. 65 = 4,875 (g)
Dap an dung la D.
3. Dé di^u chS' dirotc 78 gam Cr tir CrjOj (du) bang phuomg phap nhiSt nh6m v6i
hifiu suát cua phan irng la 90% thi kh6'i luqmg b6t nh6m cin dung t6'i thiéu la
Ạ 40,5 gam B. 81,0 gam C. 54,0 gam D. 45,0 gam
Hu&ng đn gidi
Theo bai ra: = 78/52 = I,5^mol) . 0
2A1 + C12O3 — ^ 2 C r + AI2O3
1,5 <- 1,5 mol 1 5 97 i n n
V i H = 90% nen: m ^ , = ' ' ^ j ^ = 45,0(gam)
Dap an dung la D.
4. oxi hoa hoan toan 0,01 mol CrCl, thanh K,Cr04 bang CU khi c6 mat K O H , luong t6'i thi^u va K O H tuomg iJng la
' A . 0,015 mol va 0,04 mol. B. 0,015 mol va 0,08 mol. ' C. 0,03 mol va 0,04 mol. D . 0,03 mol va 0,08 mol.
Hu&ng đn gidi
PTPlT: 2CrCl3 + BCU + 1 6 K 0 H ^ 2K2Cr04 + 12KCI + 8 H , 0 0,01 mol
Theo PTPCT: nc, 2 = 0,015 (mol)
H K O H = 8.0,01 =0,08 (mol)
Vay cin t6'i thieu 0,015 mol CI, va 0,08 mol K O H .
Dap an dung la B. 5. Trong phan utig:
K2Cr207 + HCl -> CrClj + CI2 + K C l + H j O
S6' phan tir HCl dong vai tr6 chát khir bang k Mn t6ng s6' phan tir HCl tham gia
phan utig. Gia trj ciia k la
A . 3/14 B. 1/7 C. 3/7 D . 4/7
Hu&ng đn gidi
Hoan thanh PTPLT:
K2Cr207 + 14HC1 >2CrCl3 + 2KC1 + 3CI2 + 7H2O
=> Se» phan tir H Q tham gia phan ling = 14. S6' phan tiir HCl la chat khu = 6
z:>k = 6/14 = 3/7. Dap an diing la C.
'r i :' i
6. Khi cho lucmg du dung dich K O H vao 6'ng nghifim dung dung dich kali dicromat, dung djch trong 6'ng nghiem
Ạ chuy^n tir mau vang sang mau da cam B. chuyen tijf mau vang sang mau do