Phosphoric acid reacts with zinc to produce hydrogen gas and zinc phosphate. How many grams of acid are required to produce 5.3 liters of hydrogen at 743mmHg and 27.0 degrees Celsius

Use PV = nRT and convert the gas volume to STP and solve for n. Then follow this example problem to convert moles H2 to moles H3PO4 and to grams.

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To answer this question, you need to use the ideal gas law equation and stoichiometry.

1. Start by writing the balanced chemical equation for the reaction:
2 H₃PO₄ + 3 Zn → 3 H₂ + 3 Zn₃(PO₄)₂

2. Convert the given conditions to the required units:
Volume of hydrogen gas = 5.3 liters
Pressure of hydrogen gas = 743 mmHg
Temperature of hydrogen gas = 27.0 degrees Celsius

To use the ideal gas law, the temperature must be converted to Kelvin:
Convert 27.0 degrees Celsius to Kelvin:
T(K) = 27.0 + 273.15 = 300.15 K
Pressure must also be converted to atmospheres (atm):
Pressure(atm) = 743 mmHg * (1 atm / 760 mmHg) = 0.976 atm

3. Calculate the number of moles of hydrogen gas produced using the ideal gas law equation:
PV = nRT
Where:
P = Pressure (in atm)
V = Volume (in liters)
n = number of moles
R = ideal gas constant (0.0821 L·atm/K·mol)
T = temperature (in Kelvin)

n = PV / RT
n = (0.976 atm) * (5.3 L) / (0.0821 L·atm/K·mol) * (300.15 K)

Calculate n (number of moles of hydrogen gas produced).
Note: This will be the same number of moles of acid required, considering the stoichiometry of the balanced equation.

4. Use the stoichiometry of the balanced equation to determine the number of moles of phosphoric acid required to produce the calculated amount of hydrogen gas.
According to the balanced equation:
2 moles of H₃PO₄ produces 3 moles of H₂

Therefore, the number of moles of H₃PO₄ required = (2 moles H₃PO₄ / 3 moles H₂) * n (moles of H₂)

5. Calculate the mass of phosphoric acid using its molar mass.
The molar mass of H₃PO₄ = (1*3.01 g/mol) + (1*1.01 g/mol) + (4*16.00 g/mol) = 98.00 g/mol

Mass of H₃PO₄ = (number of moles of H₃PO₄) * (molar mass of H₃PO₄)

Now, you can plug in your values and calculate the required mass of phosphoric acid.