Multiple Choice
Calculate the percent yield of CO2 when 28.16 g of CO2 are produced from the reaction of 4.000 moles of C8H18 with 4.000 moles of O2, given the reaction: 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O.
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3. Chemical Reactions
Percent Yield
Multiple Choice
Hydrogen gas (a potential future fuel) can be formed by the reaction of methane with water according to the following equation: CH4(g) + H2O(g) → CO(g) + 3H2(g). In a particular reaction, 26.5 L of methane gas (measured at a pressure of 730 torr and a temperature of 298 K) is reacted. If the actual yield of hydrogen gas is 60.0 L, what is the percent yield of hydrogen gas?
A
95.0%
B
75.0%
C
85.0%
D
90.0%
Verified step by step guidance1
First, use the ideal gas law to calculate the number of moles of methane gas (CH4) that reacted. The ideal gas law is given by the equation: \( PV = nRT \), where \( P \) is the pressure, \( V \) is the volume, \( n \) is the number of moles, \( R \) is the ideal gas constant, and \( T \) is the temperature in Kelvin.
Convert the pressure from torr to atm, since the ideal gas constant \( R \) is typically expressed in terms of atm. Use the conversion: \( 1 \text{ atm} = 760 \text{ torr} \).
Substitute the known values into the ideal gas law equation to solve for \( n \), the number of moles of CH4. Use \( R = 0.0821 \text{ L atm/mol K} \).
According to the balanced chemical equation, 1 mole of CH4 produces 3 moles of H2. Use stoichiometry to calculate the theoretical yield of hydrogen gas in moles, then convert this to volume using the ideal gas law, assuming the same conditions of temperature and pressure.
Calculate the percent yield using the formula: \( \text{Percent Yield} = \left( \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \right) \times 100 \). Substitute the actual yield (60.0 L) and the theoretical yield calculated in the previous step to find the percent yield.
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