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To understand partial pressure, think of each gas in a mixture as contributing to the total pressure. The partial pressure of a gas is the pressure it would exert if it were the only gas present in the container. In our exercise, we need to find the partial pressure of hydrogen gas \(H_2\) collected over water. The total pressure measured is the sum of the pressures exerted by \(H_2\) and the water vapor. Using the formula: \[ P_{H_2} = P_{total} - P_{H_2O} \] we subtract the vapor pressure of water (\(14 \) mmHg) from the total pressure (\(758 \) mmHg), resulting in a partial pressure of \(744 \) mmHg.

In chemistry, calculating the number of moles of a substance produced in a reaction is essential. Moles help us quantify amounts in a chemical reaction. The Ideal Gas Law, represented as \[ PV = nRT \] can be rearranged to solve for the number of moles, \(n\): \[ n = \frac{PV}{RT} \] Here, \(P\) is pressure, \(V\) is volume, \(R\) is the gas constant (0.0821 L·atm/(K·mol)), and \(T\) is temperature in Kelvin. After converting pressure from mmHg to atm, volume to liters, and temperature to Kelvin, substitute these values into the equation: \[ n = \frac{(0.9789\text{ atm})(0.425\text{ L})}{(0.0821\text{ L·atm/(K·mol)})(289.15\text{ K})} = 0.0175 \text{ moles} \] This gives us the amount of hydrogen gas produced.

Gas conversions are crucial for using the Ideal Gas Law accurately. Pressure is often measured in mmHg or atm, volume in liters or milliliters, and temperature in Celsius or Kelvin. Consistent units are vital. For pressure conversion: \[ 1 \text{ atm} = 760 \text{ mmHg} \] So, to convert \(744 \text{ mmHg}\) to atm: \[ 744 \text{ mmHg} \times \frac{1 \text{ atm}}{760 \text{ mmHg}} = 0.9789 \text{ atm} \] Volume conversion from mL to L uses: \[ 1 \text{ mL} = 0.001 \text{ L} \] For temperature conversion to Kelvin: \[ T(K) = T(^{\text{C}}) + 273.15 \] Convert \(16^{\text{C}}\) to Kelvin: \[ 16^{\text{C}} + 273.15 = 289.15 \text{ K} \] Applying these conversions ensures the correct use of the Ideal Gas Law.

Chemical reactions describe the process where reactants convert to products. In our example: \[ \text{Zn}(s) + \text{HCl}(aq) \rightarrow \text{H}_2(g) + \text{ZnCl}_2(aq) \] Zinc (\text{Zn}) reacts with hydrochloric acid (\text{HCl}) to produce hydrogen gas (\text{H}_2) and zinc chloride (\text{ZnCl}_2). Balancing chemical equations ensures that the number of atoms for each element is equal on both sides of the reaction. This balanced equation also helps in stoichiometric calculations, determining the amount of each reactant used and each product formed. Stoichiometry and gas laws help predict and measure the outcomes of chemical reactions reliably. Always ensure equations are balanced before proceeding with calculations.