Chemistry question

Question

When a .......... gas is passed in a solution of .......... no obvious change in the color of the solution occurs.

a- CO2 / Ca(OH)2

b- NH3 / NaOH

c- H2S / (CH3COO)2Pb

d- SO2 / acidified K2Cr2O7

## I need the answer with detailed steps (why)##

Answer 1

a- CO2 / Ca(OH)2 ==> CaCO3 insoluble and solutions turns cloudy white

b- NH3 / NaOH ==> No reaction. No color change. This is the answer

c- H2S / (CH3COO)2Pb ==> PbS precipitate and a color change

d- SO2 / acidified K2Cr2O7 ==> turns from orange to green. Redox reaction. Color change.