From the set up in the video for heating of Carbonates,the boiling tube must be in slanting position. The delivery tube collecting the gas must be fitted with a cork at the mouth of the boiling tube. The delivery tube must be dipped inside lime water.The flame used for heating should be non luminous flame. The first bubbles produced do not change the colour of lime water.

1). Why is the boiling tube set in a slanting position.

2). Why is the delivery tube fitted with a cork  at the mouth of the boiling tube?

3). Why should the delivery tube be dipped inside lime water.

4). Why is non luminous flame prefered.