When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter (Figure 5.18), the temperature rises from 21.6 to 37.8 °C (b) Using your result from part (a), calculate H (in kJ/mol KOH) for the solution process. Assume that the specific heat of the solution is the same as that of pure water.
Verified step by step guidance
1
Identify the mass of the sodium hydroxide (NaOH) and the water. Here, the mass of NaOH is 6.50 g and the mass of water is 100.0 g.
Calculate the total mass of the solution by adding the mass of NaOH and the mass of water.
Determine the temperature change (\(\Delta T\)) by subtracting the initial temperature from the final temperature: \(\Delta T = 37.8\, ^\circ\text{C} - 21.6\, ^\circ\text{C}\).
Use the formula for heat absorbed or released: \(q = m \cdot c \cdot \Delta T\), where \(m\) is the total mass of the solution, \(c\) is the specific heat capacity of water (4.18 J/g°C), and \(\Delta T\) is the temperature change.
Convert the heat \(q\) from joules to kilojoules, and then calculate the enthalpy change per mole of NaOH by dividing the heat by the number of moles of NaOH. Use the molar mass of NaOH to find the number of moles.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
10m
Play a video:
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enthalpy Change (ΔH)
Enthalpy change (ΔH) is the heat content change of a system at constant pressure, often measured during chemical reactions or phase changes. In this context, it represents the heat absorbed or released when sodium hydroxide dissolves in water. It is typically expressed in kJ/mol, indicating the energy change per mole of solute involved in the process.
Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. In this problem, the specific heat of the solution is assumed to be the same as that of water, which is 4.18 J/g°C. This value is crucial for calculating the heat absorbed by the solution when sodium hydroxide dissolves and the temperature changes.
Calorimetry is the science of measuring the heat of chemical reactions or physical changes. In this scenario, a coffee-cup calorimeter is used to measure the temperature change of the solution, which allows for the calculation of the heat transfer associated with the dissolution of sodium hydroxide. Understanding calorimetry principles is essential for accurately determining the enthalpy change of the solution process.
Verified step by step guidance
02:34
