Final answer:
To calculate the correct volume of H2 gas at STP, use the combined gas law. The correct volume is 7.57 ml. The moles of Hydrogen gas and the molar mass of the unknown metal cannot be calculated without additional information.
Step-by-step explanation:
To calculate the correct volume of H2 gas at STP, we can use the combined gas law. The formula is:
V2 = (P1 * V1 * T2) / (P2 * T1)
Where V1 is the initial volume of H2 gas, P1 is the initial pressure of H2 gas, T1 is the initial temperature of H2 gas, P2 is the atmospheric pressure at STP, and T2 is the temperature at STP.
Using the given values, the correct volume of H2 gas at STP can be calculated as follows:
V2 = (762 mm Hg * 77.0 ml * 273 K) / (760 mm Hg * (-240°C + 273 K))
V2 = 7.57 ml
Therefore, the correct volume of H2 gas at STP is 7.57 ml.
To calculate the moles of Hydrogen gas and the unknown metal, we need more information such as the reaction equation or the mass of the unknown metal.
To calculate the molar mass of the unknown metal, we first need to determine the number of moles of the unknown metal. Without that information, we cannot calculate the molar mass.