If the balloon had a volume of 23000 L, how many kilograms of hydrogen were needed to fill the balloon at STP

2. how is heavy water different from normal water

Can someone me with questions 15 to 17 plz.

Which ocean zone has the most abundant primary producer and why a) the abyssopelagic zone ,du to the absence of light and cold water temperatureb) the bathypelagic zone, due to the absence of light and cold water temperaturec) the mesopelagic zone ,due to uts high light availability and warm water temperature d) the epipelagic zone,due to its high light availability and warm water temperature