In this problem, we are asked to convert from one unit to another unit. To do this, we need a conversion factor to multiply to the original value. From kg to g, 1000 g is equal to 1 kg. From g to ng, 1 g is equal to 10^9 ng. We convert as follows:
2.1 kg (1000 g / 1 kg) (10^9 ng / 1 g ) = 2.1x10^12 ng sodium bicarbonate
