A copper sulfate solution is warmed by a reaction in the apparatus in Fig. 1. A technician compares the reaction of zinc powder with copper sulfate solution...
Question 1 Report
A copper sulfate solution is warmed by a reaction in the apparatus in Fig. 1. A technician compares the reaction of zinc powder with copper sulfate solution at a recycling plant. The energy released heats the solution, but some energy also warms the cup and escapes to the air. Table 1 gives the recorded results. The solution has a mass of 75 g and a specific heat capacity of 4.2 J g-1 degrees C-1.
| time after mixing / s | temperature / degrees C |
|---|---|
| 0 | 19.8 |
| 30 | 28.4 |
| 60 | 31.2 |
| 90 | 30.6 |
(a) Record the maximum temperature shown in Table 1. [1]
(b) Use the results to calculate the energy gained by the solution. [2]
(c) Describe one reason why this calculated value is less than the total energy released by the reaction. [1]
Answer Details
(a) The maximum temperature is 31.2 °C. [1]
(b) Temperature rise = 31.2 °C − 19.8 °C = 11.4 °C.
Q = mcΔT = 75 g × 4.2 J g-1 °C-1 × 11.4 °C
= 3591 J, or 3.59 × 103 J. [2]
(c) The calculated value is smaller than the total energy released because some energy warms the cup or thermometer, or is transferred to the surroundings rather than heating the solution. [1]
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