Question

1. A sample of gaseous helium is heated with an electrical coil. If 821 Joules of energy are added to a 13.4 gram sample and the final temperature is 35.7°C, what is the initial temperature of the helium?

Answer: ____ °C.

2. A sample of solid platinum is heated with an electrical coil. If 28.0 Joules of energy are added to a 14.3 gram sample initially at 23.0°C, what is the final temperature of the platinum?

Answer: ____°C

3. What is the energy change when the temperature of  13.4 grams of  gaseous helium is decreased from  35.7 °C to 23.9 °C ?

Answer: ____ Joules

Answer 1

1.

The energy added to the sample is being used to increase the temperature of the sample of gaseous Heilum.

For a monoatomic gas like Helium, the specific heat at constant pressure is given by

The heat and specific heat are related to temperature change in the following way:

Given that

Amounht of substance = 13.4 gm

Molar mass of helium = 4 g/mol

hence, number of moles, n =

gas constant, R =

Now using the relation

hence, the initial temperature is

2.

Molar heat capacity Cp of solids is generally equal to 3R.

Hence, for platinum.

Now,

Given that

Molar mass of platinum = 195 gm/mol

Amount = 14.3 gm

hence, number of moles ,n =

Now uwing the relation

hence, the final temperature is

3.

Given that

For Helium

amount = 13.4 gm

Number of moles , n =

hence, using the relation

hence, the energy change is 821.63 Joules