If a 1.85g mass of zinc produces 475 ml og gas and your balloon weighs 0.574 g and the room temperature is 20.5°c. calculate the amount of zinc needed to produce enough gas to get your balloon airborne by adding 1 ml to the required balloon volume so that its density is less than that of the surrounding air.

You will use an ideal gas equation here. Let us denote 'x' as the unknown sample of zinc if another 1 ml of it is added to make a total of 476mL gas. The ideal gas equation is PV = nRT. Assume atmospheric conditions and then substitute everything to the equation.

(1atm)(0.476L) = (1.85 + x)(0.08206 L-atm/mol-K)(20.5+273K)
x = 1.83 g of zinc

100%sorry if i’m wronghope this good luck: )