When 100.0 mL of 0.200 M NaOH is mixed with 50.0 mL of 0.400 M HF in a calorimeter, the temperature increases from 22.50 °C to 24.68 °C. Based on this temperature change, what type of reaction is occurring?

• A. Isothermal
• B. Adiabatic
• C. Exothermic
• D. Endothermic

Answer: (C)

Verified step by step guidance

1. Identify the type of reaction based on the temperature change. In this problem, the temperature increases from 22.50 °C to 24.68 °C, indicating that heat is released to the surroundings.
2. Understand the concept of exothermic reactions. An exothermic reaction is one where energy is released in the form of heat, causing the temperature of the surroundings to increase.
3. Consider the chemical reaction between NaOH and HF. When these two substances react, they form water and sodium fluoride (NaF), releasing energy in the process.
4. Recognize that an increase in temperature in a calorimeter indicates an exothermic reaction, as the system releases heat to the surroundings.
5. Conclude that the reaction between NaOH and HF is exothermic, as evidenced by the increase in temperature from 22.50 °C to 24.68 °C.