五、When a student mixes 50 mL of 1.0 M (= 1.0 mol/L) HCL and 50 mL of 1.0 M NaOH in a coffee-cup calorimeter, the temperature of the resultant solution increases from 21.0°C to 27.5°C. Calculate the enthalpy change for the reaction in kJ/mol HCl, assuming that the calorimeter loses only a negligible quantity of heat, that the total volume of the solution is 100 mL, that its density is 1.0 g/mL, and that its specific heat is 4.18 J/g-K.

二、The figure below shows an accident. Car A slid into the rear of car B,which was stopped at a red light along a road headed down a hill. Theslope of the hill is . The cars were separated by distancem when the driver of car A put the car into a slide (it lackedany automatic anti-brake-lock system), and that the speed of car A at theonset of braking was m/s. With what speed did car A hit carB if the coefficient of kinetic friction was 0.60? 【Hint】: 1. the magnitude of the free-fall acceleration $g = 9.8 \, \mathrm{m/s}^2$ . 2. $\sin 12^{\circ} \approx 0.20$ ; $\cos 12^{\circ} \approx 0.98$ . 3. $v = v_{0} + at$ . 4. $S = v_{0}t + \frac{1}{2} at^{2}$ . 5. v2= v02 + 2aS .

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