Cl,Br,I

Question 1

1)Cl- + KMnO4—->
2)Cl- + PbO2—->
3)Cl- + MnO2 —>

Answer 1

1)Cl- + KMnO4—->Mn+2 + Cl2
2)Cl- + PbO2—->PbCl2 + Cl2
3)Cl- + MnO2 —>Mn+2 + Cl2

Question 2

4)chromyl chloride test for Cl-:

Answer 2

K2Cr2O7 + KCl + conc.H2SO4 —->H2CrO4—->CrO3—Cl—->CrO2Cl2(Red-orange vapors)
CrO2Cl2—-NaOH—->Na2CrO4(yellow)—Pb+2—->PbCrO4(yellow)

Question 3

1)Br- + conc.H2SO4 —-> —NaOH—->
2)NO3- + conc.H2SO4—-> —NaOH—->NaNO3 + NaNO2

Answer 3

1)Br- + conc.H2SO4 —->Br2 —NaOH—->NaBr + NaOBr(yellow due to Br2)
2)NO3- + conc.H2SO4—->NO2 —NaOH—->NaNO3 + NaNO2(yellow due to NO2)

Question 4

1)KMnO4/H+ + Br- —->
2)conc. HNO3 + Br- —->
3)PbO2 + Br- —>
4)MnO2 + Br- —->
5)CaOCl2 + Br- —->

Answer 4

1)KMnO4/H+ + Br- —->Mn+2 + Br2
2)conc. HNO3 + Br- —->NO2 + Br2
3)PbO2 + Br- —>Pb+2 + Br2
4)MnO2 + Br- —->Mn+2 + Br2
5)CaOCl2 + Br- —->Cl- + Br2

Question 5

layer test for Br-,I-

Answer 5

1)Cl2 + KBr—->Br2 + KCl —CCl4—->CCl4(ppt) +Br2(ppt) [red] + KCl
2)Cl2 + KI—->KI3 + KCl —CCl4—->I2(ppt) + CCl4(ppt) [purple] + KCl

Question 6

gives brown color with KI due to formation of KI3
gives blue color with starch

Question 7

1)KMnO4/H+ + I- —->
2)HNO2 + I- —->
3)PbO2 + I- —->
4)conc.HNO3 + I- —->
5)H2O2/H+ + I- —->
6)K3Fe(CN)6 +KI(excess)—->
7)KMnO4 + I- —->

Answer 7

1)KMnO4/H+ + I- —->Mn+2 + I2
2)HNO2 + I- —->NO + I2
3)PbO2 + I- —->Pb+2 + I2
4)conc.HNO3 + I- —->NO2 + I2
5)H2O2/H+ + I- —->H2O + I2
6)K3Fe(CN)6 +KI(excess)—->K4Fe(CN)6
7)KMnO4 + I- —->OH- + MnO2 + IO3-(I- —->I2—OH—>I- + IO3-