6. During aeration, a cylindrical reactor had a height of 10 m. Without aeration, the height was 7.5 m. Under these aeration and mixing conditions, the gas hold up in the reactor is
7. A cylindrical reactor has a liquid volume of 100,000 litres. It has an aspect ratio the ratio of the channel height to width of 1:1. The height of the liquid in the reactor will be approximately: