26.0 g of copper pellets are removed from a 300∘C oven and immediately dropped into 120 mL of water at 21.0 ∘C in an insulated cup.What will the new water temperature be?

Respuesta :

Answer:

The new water temperature is 26.4 °C

Explanation:

Given;

mass of copper, [tex]M_{cu}[/tex] = 26 g = 0.026 kg

temperature of copper, t = 300 °C

volume of water, V = 120 mL = 0.12 L

temperature of water, t = 21 °C

density of water, ρ = 1 kg/L

mass of water = density x volume

mass of water = (1 kg/L) x 0.12 L = 0.12 kg

heat lost by copper = heat gained by water

Both copper and water reach final temperature, T

Heat gained by water, [tex]Q_w[/tex] = [tex]m_w[/tex]cΔθ = [tex]m_w C(T - t)[/tex]

[tex]Q_w = m_w C(T - t)\\\\Q_w = 0.12*4200(T-21)\\\\Q_w = 504(T-21)[/tex]

Heat lost by copper is given by;

[tex]Q_{cu} = m_{cu}C(300-T)\\\\Q_{cu} = 0.026*385(300-T)\\\\Q_{cu} = 10.01(300 - T)[/tex]

[tex]Q_{cu} = Q_w[/tex]

504(T- 21) = 10.01(300 - T)

504 T - 10584 = 3003 - 10.01 T

504 T + 10.01 T= 3003 + 10584

514.01 T = 13587

T = (13587) / 514.01

T = 26.4 °C

Therefore, the new water temperature is 26.4 °C

The new water temperature using the given parameters is;

26.49°C

We are given;

Mass of copper; m_cu = 26 g = 0.026 kg

Temperature; T_cu = 300 °C

Volume of water; V = 120 mL = 0.12 L

Temperature of water, T_w = 21 °C

Density of water; ρ = 1 kg/L

Let us find the mass of water from the formula;

m_w = ρ × V

m_w = 1 × 0.12

m_w = 0.12 kg

Now, from the principle of conservation of energy, we can say that the total heat lost by a hot body is equal to the total heat gained by a cold body.

The hot body here is copper while the cold body is water. Thus;

Heat lost by copper = Heat gained by water

Formula for heat lost by copper is;

Q_cu = m_cu * c_cu * (T_f - T_cu)

Formula for heat gained by water is;

Q_w = m_w * c_w * (T_f - T_w)

Where;

T_f is final temperature reached by copper and water

c_cu is specific heat capacity of copper = 385 J/kg.°C

c_w is specific heat capacity of water = 4200 J/kg.°C

Thus;

Q_cu = 0.026 × 385 × (300 - T_f)

Q_cu = 3030 - 10.01T_f

similarly;

Q_w = 0.12 × 4200 × (T_f - 21)

Q_w = 504T_f - 10584

Thus;

3030 - 10.01T_f = 504T_f - 10584

3030 + 10584 = 504T_f + 10.01T_f

13614 = 514.01T_f

T_f = 13614/514.01

T_f = 26.49°C

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