To identify the process in which V2O5 (Vanadium(V) oxide) is used as a catalyst.

• The Solvay process is used to produce sodium carbonate and does not typically use $\text{V}_2\text{O}_5$ as a catalyst.
• The Haber process synthesizes ammonia from nitrogen and hydrogen, using finely divided iron as a catalyst.
• The Contact process is used for the industrial production of sulfuric acid. A key step in this process is the oxidation of sulfur dioxide ($\text{SO}_2$) to sulfur trioxide ($\text{SO}_3$), which is catalyzed by $\text{V}_2\text{O}_5$.
• The Ostwald process is used to produce nitric acid from ammonia, using a platinum-rhodium alloy as a catalyst.

Based on the information above, $\text{V}_2\text{O}_5$ is the catalyst used in the Contact process.

The final answer is $\text{C. Contact process}$