If you pour whisky over ice, the ice will cool the drink, but it will also dilute it. A solution is to use whisky stones. Suppose Ernest pours 55.0 g of whisky at 22 ∘C room temperature, and then adds three whisky stones to cool it. Each stone is a 32.0 g soapstone cube that is stored in the freezer at -11 ∘C. The specific heat of soapstone is 980 J/kg⋅K; the specific heat of whisky is 3400 J/kg⋅K.What is the final temperature of the whisky?

Respuesta :

Answer:

10.1 °C

Explanation:

After the mixture, heat is gained by the soapstone cubes (they were at a lower temperature) while heat is lost by the whisky (it was at a higher temperature).

Let the temperature of the mixture be T.

Heat lost by whisky, [tex]H_W = m_Wc_W\Delta\theta_W[/tex]

[tex]m_W[/tex] is the mass of the whisky (in kg), [tex]c_W[/tex] is the specific heat of whisky (J/kg·K) and [tex]\Delta\theta_W[/tex] is the change in temperature of the whisky (in °C or K).

[tex]H_W = (0.055\text{ kg})(3040\text{ J/kg}\cdot\text{K})(22-T) = 167.2(22-T) \text{ J}[/tex]

Heat gained by soapstone cubes, [tex]H_C = m_Cc_C\Delta\theta_C[/tex]

There are three cubes of soapstone, so their mass is multiplied by 3.

[tex]H_W = (3\times0.032\text{ kg})(980\text{ J/kg}\cdot\text{K})(T-(-11)) = 94.08(T+11) \text{ J}[/tex]

From the principle of mixtures,

Heat lost by whisky = Heat gained by soapstone cubes (assuming no heat loss to the surroundings)

[tex]167.2(22-T) = 94.08(T+11)[/tex]

[tex]3678.4 - 167.2T = 94.08T + 1034.88[/tex]

[tex]2643.52 = 261.28T[/tex]

[tex]T= 10.1[/tex]

The final temperature of the whisky is 10.1 °C.

The final temperature is 10.95 °C.

When two bodies at different temperature come into contact, heat flows from the hotter body to the cooler body until thermal equilibrium is achieved between the two bodies.

Given that;

Heat lost by hot drink = Heat gained by whisky stones

Let the final temperature be θf

Heat lost by hot drink = mcθ

m = 55.0 g

c =  3400 J/kg⋅K

θ = 22 - θf

H =  55.0 × 3400 × (22 - θf)

Heat gained by whisky stones =  mcθ

m = 3(32.0 g)

c =  980 J/kg⋅K

θ = θf - (-11)

H = 96 × 980  × (θf - (-11))

Hence;

55.0 × 3400 × (22 - θf) = 96 × 980  × (θf - (-11))

4114000 - 187000θf = 94080θf  + 1034880

4114000 - 1034880 = 94080θf +  187000θf

3079120 = 281080θf

θf = 3079120/281080

θf = 10.95 °C

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