Please describe the lab preparation of hydrogen.

what are upward displacement of air, downward displacement of water and why are they not used to collect hydrogen

 Why Pure Zinc is not used to prepare hydrogen

why air is necessary for burning

Hydrogen is the lightest gas then why do we use helium in weather baloons and decorating baloons?

WELL this is not a study related Question can I know the online teachers name?

please send the answer as soon as possible...

 Why Hydrogen is placed separately in the periodic table ?( The reason given in the chapter is that Hydrogen cannot exist freely. But there are many other elements which do not exist freely but they are not separetely placed in the periodic table.)

what is meant by downward displacement of water

 what is electrolysis of water?

 Why hydrogen is collected by downward displacement of water ? Give five reasons?

what happens when iodine crystals are heated

 why H₂ does not support combustion and why is it insoluble in water?

 give the various values of universal gas constant.

why?

Why Hydrogen is neutral towards litmus paper?

 the formula represents what name?HNO3,KOH,NAOH,PbBr2.

what is electrolysis of water????