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Current Question (ID: 8292)
Question:
$\text{The work done in ergs for the reversible expansion of one mole of an ideal gas from a volume of 10 liters to 20 liters at } 25^{\circ}\text{C is -}$
Options:
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1. $-2.303 \times 298 \times 0.082 \log 2$
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2. $-298 \times 10^7 \times 8.31 \times 2.303 \log 2$
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3. $2.303 \times 298 \times 0.082 \log 0.5$
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4. $-8.31 \times 10^7 \times 298 - 2.303 \log 0.5$
Solution:
$\text{Hint: } W = -2.303 \text{ nRT}\log \frac{V_2}{V_1}$
$\text{Step 1: Identify the given values}$
$\text{The given values are as follows:}$
$V_1 = 10 \text{ L (initial volume)}$
$V_2 = 20 \text{ L (final volume)}$
$n = 1 \text{ mol (number of moles)}$
$T = 25^{\circ}\text{C} = 273 + 25 = 298 \text{ K (temperature)}$
$R = 8.314 \text{ J mol}^{-1}\text{K}^{-1} \text{ (gas constant)}$
$\text{Conversion factor: } 1 \text{ J} = 10^7 \text{ erg}$
$\text{Therefore, } R = 8.314 \times 10^7 \text{ erg mol}^{-1}\text{K}^{-1}$
$\text{Step 2: Apply the formula for work done in reversible isothermal expansion}$
$\text{For a reversible isothermal expansion of an ideal gas, the work done is given by:}$
$W = -nRT\ln\frac{V_2}{V_1}$
$\text{Using base-10 logarithm: } W = -2.303 \times nRT\log\frac{V_2}{V_1}$
$W = -2.303 \times 1 \times 8.314 \times 10^7 \times 298 \times \log\frac{20}{10}$
$W = -2.303 \times 8.314 \times 10^7 \times 298 \times \log 2$
$\text{Rearranging: } W = -298 \times 10^7 \times 8.314 \times 2.303 \times \log 2$
$\text{Step 3: Verify the answer}$
$\text{The negative sign indicates that the gas is doing work on the surroundings during expansion.}$
$\text{The answer matches option 2: } -298 \times 10^7 \times 8.31 \times 2.303 \log 2$
$\text{Note: There's a slight difference in the value of R (8.31 vs. 8.314), but this is within acceptable rounding for multiple-choice options.}$
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