Selina Solutions Class 9 Chemistry Solutions for Exercise 6B in Chapter 6 - Chapter 6 Study Of The First Element Hydrogen

Question 1 Exercise 6B

a) Name the impurities present in hydrogen prepared in the laboratory.

b) How can these impurities be removed?


a) Hydrogen sulphide, sulphur dioxide, oxides of nitrogen, phosphine, arsine, carbon dioxide and

water vapour are the impurities present in the hydrogen prepared in the laboratory.

b) The impurities can be removed from hydrogen by passing it through

  1. Silver nitrate solution to remove arsine and phosphine.

AsH3 + 6AgNO3 → Ag3As + 3AgNO3 + 3HNO3

PH3 + 6AgNO3 → Ag3P + 3AgNO3 + 3HNO3

  1. Lead nitrate solution to remove hydrogen sulphide.

Pb(NO3)2 + H2S → PBS + 2HNO3

  1. Caustic potash solution to remove sulphur dioxide, carbon dioxide and oxides of nitrogen.

SO2 + 2KOH → K2SO3 + H2O

CO2 + 2KOH→ K2CO3+ H2O

2NO2 + 2KOH →KNO2 + KNO3 + H2O

  1. A drying agent used to dry the gas. Common drying agents such as fused calcium chloride, caustic potash stick and

phosphorus pentoxide removes water vapour.

So, the gas is purified and dried and then collected over mercury because mercury does not react with it.

Video transcript
[Music] hello dear student i am sunita nair from vedo learning let's answer this question name the impurities which are present in hydrogen prepared in the laboratory so when hydrogen is prepared in the laboratory certain impurities are also byproducts so the thing is how can we remove these impurities so let's list out the impurities and also give their neutralizing agents that is what can get rid of those impurities for us so the first impurity and these are in no particular order we have the we have ph 3 and as h3 right these are phosphene phosphine gas and are seen gas now all the impurities are of course gases so they have to be neutralized into either a solid precipitate or a liquid that can be that will not have any effect on the hydrogen gas so we have phosphene and arsine which can be neutralized by [Music] lead night i am sorry a silver nitrate right so these two can be taken care of by the addition of silver nitrate whose formula is ag no3 then the next set of impurities are oxides right we have oxides of sulfur that is sulfur dioxide we have carbon dioxide and we have oxides of nitrogen which is no2 right so we have here sulphur dioxide carbon dioxide and oxides of nitrogen apparently there is more than one oxide of nitrogen so now these three will be neutralized by right and these three will be taken care of by the addition of caustic potash which is k o h and finally we have the impurity which is hydrogen sulfide gas h2s hydrogen sulfide gas which can be neutralized by the addition of lead nitrate whose formula is lead pb no3 2. right so this is how all these impurities can be taken care of and finally when all these impurities have been removed a drying agent the gas is passed through a drying agent which may be drying agent which may be fused calcium chloride any of these right fused calcium chloride or even potassium pentoxide or even a potash caustic potash stick right so these are the drying agents so it is important that the gas is passed through a drying agent also and finally it is collected over mercury this dried and purified gas is collected over mercury the dried and purified gas or should i say the purified and dried gas because first it was purified and then it was dried is collected over mercury because it does not react with mercury so i hope this answers the question satisfactorily do drop in a comment if you have any doubts visit our channel for more homework solutions like this and subscribe to lido for updates as well thank you
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