A silver cube with an edge length of 2.36 cm and a gold cube with an edge length of 2.67 cm are both heated to 87.9 ∘C and placed in 108.0 mL of water at 19.7 ∘C . What is the final temperature of the water when thermal equilibrium is reached?

Respuesta :

Answer:

Hence, the final temperature is 28.3 °C .

Explanation:

Given, the edge length of the silver cube = 2.36 cm

The volume of the silver cube = [tex](Edge/ length)^3[/tex] = [tex](2.36)^3[/tex] cm³ = 13.144256 cm³

Given, the edge length of the gold cube = 2.67 cm

The volume of the gold cube = [tex](Edge/ length)^3[/tex] = [tex](2.67)^3[/tex] cm³ = 19.034163 cm³

Density is defined as:-

[tex]\rho=\frac{Mass}{Volume}[/tex]

or,  

[tex]Mass={\rho}\times Volume[/tex]

So, Density of silver = 10.5 g/cm³

Thus, Mass of the silver cube = 10.5 g/cm³ * 13.144256 cm³ = 138.0147 g

So, Density of gold = 19.3 g/cm³

Thus, Mass of the gold cube = 19.3 g/cm³ * 13.144256 cm³ = 253.6841 g

So, Density of water = 1 g/cm³

Given, Volume = 108.0 mL = 108.0 cm³

Thus, Mass of the water = 1 g/cm³ * 108.0 cm³ = 108.0 g

Heat gain by water = Heat lost by gold + Heat lost by silver

Thus,  

[tex]m_{water}\times C_{water}\times (T_f-T_i)=-m_{gold}\times C_{gold}\times (T_f-T_i)-m_{silver}\times C_{silver}\times (T_f-T_i)[/tex]

Where, negative sign signifies heat loss

Or,  

[tex]m_{water}\times C_{water}\times (T_f-T_i)=m_{gold}\times C_{gold}\times (T_i-T_f)+m_{silver}\times C_{silver}\times (T_i-T_f)[/tex]

For water:

Mass = 108.0 g

Initial temperature = 19.7 °C

Specific heat of water = 4.184 J/g°C

For gold:

Mass = 253.6841 g

Initial temperature = 87.9 °C

Specific heat of water = 0.1256 J/g°C

For silver:

Mass = 138.0147 g

Initial temperature = 87.9 °C

Specific heat of water = 0.2386 J/g°C

So,  

[tex]108.0\times 4.184\times (T_f-19.7)=253.6841\times 0.1256\times (87.9-T_f)+138.0147\times 0.2386\times (87.9-T_f)[/tex]

[tex]108\times \:4.184\left(T_f-19.7\right)=31.86272296\left(-T_f+87.9\right)+32.93030742\left(-T_f+87.9\right)[/tex]

[tex]451.872T_f-8901.8784=5695.30737 -64.79303038T_f[/tex]

[tex]516.66503 T_f=14597.18577[/tex]

[tex]T_f=\frac{14597.18577}{516.66503}[/tex]

[tex]T_f = 28.25270\ ^0C[/tex]

Hence, the final temperature is 28.3 °C .

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