Question

"When a 3.00-g sample of KCl was added to 3.00 × 10^2

g of water in a coffee cup calorimeter, the
temperature decreased by 1.05 °C. How much heat is involved in the dissolution of the KCl? What
assumptions did you make?"

Answer 1

The heat involved in the dissolution of KCl can be calculated using the formula ΔQ = mcΔT, where m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature. Assuming the specific heat capacity of water is 4.18 J/g ℃, the heat involved in the dissolution of KCl is -1.38 x 10³ J.

Step-by-step explanation:

The amount of heat involved in the dissolution of KCl can be calculated using the formula: ΔQ = mcΔT, where ΔQ is the heat transferred, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature. In this question, we are given the mass of KCl (3.00 g), the mass of water (3.00 x 10^2 g), and the change in temperature (-1.05 ℃). However, specific heat capacity is not provided. Assuming the specific heat capacity of water is 4.18 J/g ℃, the heat involved in the dissolution of KCl can be calculated as follows:

ΔQ = mcΔT = (3.00 x 10^2 g) * (4.18 J/g ℃) * (-1.05 ℃) = -1.38 x 10³ J

Answer 2

The amount of heat involved in the dissolution of a 3.00-g sample of KCl in water is calculated using the formula q = mcΔT, considering the specific heat of water and temperature change. The process is endothermic, indicated by the positive value of q.

Step-by-step explanation:

When a 3.00-g sample of KCl is dissolved in 3.00 × 102 g of water causing a temperature decrease by 1.05 °C, the amount of heat involved in the dissolution of KCl can be calculated using the formula q = mcΔT, where q is the heat absorbed or released, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the temperature change.

The mass (m) of the water is 3.00 × 102 g, the specific heat capacity (c) of water is 4.184 J/g°C, and the temperature change (ΔT) is -1.05 °C. Thus, q = (3.00 × 102 g) × (4.184 J/g °C) × (-1.05 °C). The negative sign for ΔT indicates that the water is losing heat, which means the process is endothermic and the heat q will have a positive value, confirming that the dissolution of KCl is indeed an endothermic process.

Assumptions: It is assumed that the calorimeter absorbs a negligible amount of heat and that the specific heat of the solution remains the same as that of pure water throughout the temperature change. This would mean that the heat calculated from the formula is entirely due to the dissolution of KCl.