Thermodynamics CBSE Questions & Answers

Which of the following is not correct?

When gasoline burns in a car engine, the heat released causes the products \({\text{C}}{{\text{O}}_{\text{2}}}\)andH20 to expand, which pushes the pistons outward. Excess heat is removed by the car’s cooling system. If the expanding gases do 451 J of work on the pistons and the system loses 325 J to the surroundings as heat, calculate the change in energy (\(\Delta {\text{E}}\))

For the reaction \({{\text{H}}_{\text{2}}}\left( {\text{g}} \right)\)+ \(\frac{1}{2}\) \({{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ }} \to {\text{ }}{{\text{H}}_{\text{2}}}0\left( {\text{l}} \right){\text{ }} + \) 285.8 kJ state whether exothermic and enthalpy change

For the reaction 40.7 kJ + \({{\text{H}}_{\text{2}}}0\left( {\text{l}} \right){\text{ }} \to {\text{ }}{{\text{H}}_{\text{2}}}0\) (g state whether exothermic and enthalpy change

A layer of copper welded to the bottom of a skillet weighs 125 g. How much heat is needed to raise the temperature of the copper layer from 25\(^\circ {\text{C}}\) to 300. \(^\circ {\text{C}}\)? The specific heat capacity (c) of Cu is 0.387 J/g.K.

You place 50.0 mL of 0.500 M NaOH in a coffee-cup calorimeter at 25.00\(^\circ {\text{C}}\) and carefully add 25.0 mL of 0.500 M HCI, also at 25 .00\(^\circ {\text{C}}\). After stirring, the final temperature is 27.21\(^\circ {\text{C}}\). Calculate \({{\text{q}}_{{\text{soln}}}}\) (in J) and \(\Delta {{\text{H}}_{{\text{rxn}}}}\) (in kJ/mol). (Assume the total volume is the sum of the individual volumes and that the final solution has the same density and specific heat capacity as water: d = 1 .00 g/mL and C = 4. 184 J/g·K.)

A cylinder confines 2.00 L gas under a pressure of 1.00 atm. The external pressure is also 1.00 atm. The gas is heated slowly, with the piston sliding freely outward to maintain the pressure of the gas close to 1.00 atm. Suppose the heating continues until a final volume of 3.50 L is reached. Calculate the work done on the gas.

Suppose a 10.00-kg mass drops through a height difference of 3.00 m, and the resulting work is used to turn a paddle in 200.0 g water, initially at 15.00\(^\circ {\text{C}}\). The final water temperature is found to be 15.35\(^\circ {\text{C}}\). Assuming that the work done is used entirely to increase the water temperature, calculate the conversion factor between joules and calories.

Standard Molar Enthalpy of Formation is

Suppose that 1.00 kJ of heat is transferred to 2.00 mol argon (at 298 K, 1 atm). What will the final temperature Tf be if the heat is transferred at constant volume?

Suppose that 1.00 kJ of heat is transferred to 2.00 mol argon (at 298 K, 1 atm). What will the final temperature Tf be if the heat is transferred at constant pressure?

Red phosphorus reacts with liquid bromine in an exothermic reaction \({\text{2 P}}\left( {\text{s}} \right){\text{ }} + {\text{ 3 B}}{{\text{r}}_{\text{2}}}\left( {\text{l}} \right){\text{ }} \to {\text{ 2PB}}{{\text{r}}_{\text{3}}}\left( {\text{g}} \right)\Delta {\text{H }} = {\text{ }} - {\text{243 kJ}}\) Calculate the enthalpy change when 2.63 g phosphorus reacts with an excess of bromine in this way.

To vaporize 100.0 g carbon tetrachloride at its normal boiling point, 349.9 K, and P =1 atm, 19.5 kJ of heat is required. Calculate \(\Delta {{\text{H}}_{{\text{vap}}}}\) for \({\text{CC}}{{\text{l}}_{\text{4}}}\).

Calculate the heat and the work associated with a process in which 5.00 mol of gas expands reversibly at constant temperature T = 298 K from a pressure of 10.00 to 1.00 atm

Suppose 5.00 mol of an ideal monatomic gas at an initial temperature of 298 K and pressure of 10.0 atm is expanded adiabatically and reversibly until the pressure has decreased to 1.00 atm. Calculate the enthalpy change, and the work done.