A piece of glass with a mass of 32.50 g specific heat of 0.840 J/g*°C and an initial temperature of 115 °C was dropped into a calorimeter containing 57 g of water (specific heat 4.184 J/g*°C). The final temperature of the glass and water in the calorimeter was 119.2 °C. What was the initial temperature of the water?

39.84°C
79.68°C
119.84°C
139.68°C

Respuesta :

Answer : The final temperature of water is, [tex]119.84^oC[/tex]

Solution :

[tex]Q_{absorbed}=Q_{released}[/tex]

As we know that,  

[tex]Q=m\times c\times \Delta T=m\times c\times (T_{final}-T_{initial})[/tex]

[tex]m_1\times c_g\times (T_{final}-T_2)=-[m_2\times c_w\times (T_{final}-T_1)][/tex]          .................(1)

where,

[tex]m_1[/tex] = mass of glass = 32.50 g

[tex]m_2[/tex] = mass of water = 57 g

[tex]T_{final}[/tex] = final temperature  of water and glass = [tex]119.2^oC[/tex]

[tex]T_2[/tex] = initial temperature of water = ?

[tex]T_1[/tex] = initial temperature glass = [tex]115^oC[/tex]

[tex]c_w[/tex] = specific heat of water = [tex]4.184J/g^oC[/tex]

[tex]c_g[/tex] = specific heat of glass = [tex]0.840J/g^oC[/tex]

Now put all the given values in equation (1), we get

[tex]m_1\times c_g\times (T_{final}-T_2)=-[m_2\times c_w\times (T_{final}-T_1)][/tex]

[tex](32.50g)\times (0.840J/g^oC)\times (119.2^oC-115^oC)=-[(57g)\times (4.184J/g^oC)\times (119.2^oC-T_1)][/tex]

[tex]T_1=119.84^oC[/tex]

Therefore, the final temperature of water is, [tex]119.84^oC[/tex]