Q. How much time (in a minute) is usually required for the passing of Co2 through the mould?
✅ Correct Answer: (A)
one
Explanation: in co2 moulding, mould of sand is hardened by passing of co2 for about one minute. the co2 gas forms a weak acid that hydrolyzes the sodium silicate (na2o, sio2) solution to form amorphous silica gel which acts as the bond and sodium silicate itself also provides some bonding action.