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Hi. Chat is down. Does anyone understand this?

Zinc reacts with nitric acid to make hydrogen gas and zinc chloride. If 8.4 L of hydrogen gas is formed (at STP), how many grams of zinc were reacted?

(Balance the equation before proceeding)

__Zn + __HNO3  -->  __H2 + __Zn(NO3)2



Or this?







 Sodium bicarbonate reacts with phosphroic acid to form sodium phosphate, water, and carbon dioxide gas. If 8.1 L of carbon dioxide gas is formed (at STP), how many grams of phosphoric acid reacted? (Balance the equation before proceeding)

__NaHCO3 + __H3PO4 --> __Na3PO4 + __H2O  +  __CO2





  Please, can someone help me with the Chemistry???