A 1.90-mol sample of hydrogen gas is heated at constant pressure from 306 K to 410 K. (a) Calculate the energy transferred to the gas by heat. 5.747 kJ Correct: Your answer is correct. (b) Calculate the increase in its internal energy. 4.105 kJ Correct: Your answer is correct. (c) Calculate the work done on the gas. -1.642 kJ Correct: Your answer is correct.

a. Q = 5.711 kJ

b. ΔE = 4.051 kJ

c. W = -1.660 kJ

Explanation:

1a. The amount of energy transferred to a gas when heated at constant pressure is given as Q = nCpΔT

where n = number of moles of gas;

Cp = molar specific heat of the gas at constant pressure,

ΔT = temperature change

From the given data; n = 1.90 moles , Cp of hydrogen gas (from tables) = 28.9 J/mol/K, ΔT = 104 K

Substituting the given values:

Q = 1.90 * 28.9 * 104

Q = 5710.64 J

Q = 5.711 kJ

b. The change in internal energy of a confined gas that undergoes a temperature change due to any process is given by the formula: ΔE = nCvΔT

where  n = number of moles of gas;

Cv = molar specific heat of the gas at constant volume,

ΔT = temperature change

From the given data; n = 1.90 moles , Cv of hydrogen gas (from tables) = 20.4 J/mol/K, ΔT = 104 K

substituting the values

ΔE = 1.90 * 20.5 * 104

ΔE = 4050.8 J

ΔE = 4.051 kJ

c. From the first law of thermodynamics, ΔE = Q + W

where W is work done on the system.

from our calculations, ΔE = 4.051 kJ, Q = 5.711 kJ

W = ΔE - Q

W = (4.051 - 5.711) kJ

W = -1.660 kJ

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.