For reversible expansion of an ideal gas, the work done is given by:
\[
W = nRT \log \left( \frac{V_f}{V_i} \right)
\]
Substituting the values for \( n = 1 \), \( T = 298 \, \text{K} \), \( R = 0.082 \, \text{L·atm/mol·K} \), and \( V_f = 20 \, \text{L} \), \( V_i = 10 \, \text{L} \), the work done is:
\[
W = 2.303 \times 298 \times 0.082 \log 2
\]
Final Answer:
\[
\boxed{2.303 \times 298 \times 0.082 \log 2}
\]