Numa máquina térmica uma parte da energia térmica fornecida ao sistema(Q1) é transformada em trabalho mecânico (τ) e o restante (Q2) é dissipado, perdido para o ambiente.
sendo:
τ: trabalho realizado (J) [Joule]
Q1: energia fornecida (J)
Q2: energia dissipada (J)
temos: τ = Q1 - Q2
O rendimento (η) é a razão do trabalho realizado pela energia fornecida:
η= τ/Q1
Exercícior resolvido:
Uma máquina térmica cíclica recebe 5000 J de calor de uma fonte quente e realiza trabalho de 3500 J. Calcule o rendimento dessa máquina térmica.
solução:
τ=3500 J
Q1=5000J
η= τ/Q1
η= 3500/5000
η= 0,7 ou seja 70%
Energia dissipada será:
τ = Q1 - Q2
Q2 = Q1- τ
Q2=5000-3500
Q2= 1500 J
Exercicio: Qual seria o rendimento se a máquina do exercicio anterior realizasse 4000J de trabalho com a mesma quantidade de calor fornecida ? Quanta energia seria dissipada agora?
obs: Entregar foto da resolução ou o cálculo passo a passo na mensagem
<span>When you add ice to hot water, some of the water’s heat melts the ice. The remaining heat warms the ice-cold water but cools the hot water in the process. You can calculate the mixture’s final temperature if you know how much hot water you started with, along with its temperature and how much ice you added. Two physical properties -- the specific heat and the heat of fusion -- determine exactly how the ice melts and the water cools.</span>
Answer : The mass of arsenic present in 5.0 g of orpiment is, 1.5 grams.
Explanation : Given,
Mass of orpiment = 5.0 g
As we know that the molar mass of 
is, 246.02 g/mol and the molar mass of As is, 75 g/mol.
As per the question, we conclude that:
As, 246.02 g of contains mass of arsenic = 75 g
So, 5.0 g of contains mass of arsenic = 
Thus, the mass of arsenic present in 5.0 g of orpiment is, 1.5 grams.
Answer : The pressure it exert under these new conditions will be, 87 atm
Explanation :
Combined gas law is the combination of Boyle's law, Charles's law and Gay-Lussac's law.
The combined gas equation is,
where,
= initial pressure of gas = 19 atm
= final pressure of gas = ?
= initial volume of gas = 100 L
= final volume of gas = 20 L
= initial temperature of gas = 
= final temperature of gas = 
Now put all the given values in the above equation, we get:
Therefore, the pressure it exert under these new conditions will be, 87 atm
