The alveoli are surrounded<span> by tiny blood vessels, called capillaries. The </span>alveoli<span> and capillaries both have very thin walls, which allow the oxygen to pass from the </span>alveoli<span>to the blood. The capillaries then connect to larger blood vessels, called veins, which bring the oxygenated blood from the lungs to the heart.</span>
Answer:
We normally separate unreacted hydrogen from ammonia (product) in Haber process. The reaction mixture contains some ammonia, plus a lot of unreacted hydrogen and nitrogen. The mixture is cooled and compressed, causing the ammonia gas to condense into a liquid.
It is called convection. When warm air, or current, moves up and disperse outwards as cold air, or current, moves into the warmer region.
