contestada

How much ice (at 0°C) must be added to 1.90 kg of water at 79 °C so as to end up with all liquid at 8 °C? (ci = 2000 J/(kg.°C), cw = 4186 J/(kg.°C), Lf= 3.35 Ă— 10 5 J/kg, Lv= 2.26 Ă— 10 6 J/kg) kg

Respuesta :

m = mass of the ice added = ?

M = mass of water = 1.90 kg

[tex]c_{w}[/tex] = specific heat of the water = 4186 J/(kg ⁰C)

[tex]c_{i}[/tex]  = specific heat of the ice = 2000 J/(kg ⁰C)

[tex]L_{f}[/tex] = latent heat of fusion of ice to water = 3.35 x 10⁵ J/kg

[tex]T_{ii}[/tex]  = initial temperature of ice = 0 ⁰C

[tex]T_{wi}[/tex] = initial temperature of water = 79 ⁰C

T = final equilibrium temperature = 8 ⁰C

using conservation of heat

Heat gained by ice = Heat lost by water

m [tex]c_{w}[/tex]  (T - [tex]T_{ii}[/tex] ) + m [tex]L_{f}[/tex]  = M [tex]c_{w}[/tex]  ([tex]T_{wi}[/tex] - T)

inserting the values

m (4186) (8 - 0) + m (3.35 x 10⁵ ) = (1.90) (4186) (79 - 8)

m = 1.53 kg

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