Question

A flashlight battery is hooked to a toy motor, and then the battery and the connections are sprayed with a water-proof coating. The battery is immersed in a beaker holding 100 mL of water. When the toy motor drives a device that raises a weight of 1.00 kg a distance of 10.0 m, the temperature of the water falls by 0.024 C. Assuming that the heat capacity of the battery is negligible compared to that of the water, Calculate the change in the energy of the battery contents as a result of the chemical reaction that took place in the battery.

Answer 1

Step-by-step explanation:

Formula to calculate work done by motor is as follows.

Work done by motor =
`mass * g * height`

where, g = gravitational constant = 10
`m/s^(2)`

Therefore, work done by motor is as follows.

Work done by motor =
`1.00 kg * 10 m/s^(2) * 10.0 m`

= 100.0 J

Now, heat lost by water will be calculated as follows.

q =
`mC * \Delta T`

=
`g * 4.184 J/g^(o)C * 0.024^(o)C`

= 10.0 J

Hence, heat gained by motor = heat lost by water

As, heat gained by motor = 10.0 J

So, change in energy = heat gained - work done

Therefore, change in energy will be calculated as follows.

Change in energy = heat gained - work done

= (10.0 J) - (100.0 J)

= -90.0 J

Thus, we can conclude that change in the energy of the battery contents is -90.0 J.