An insulated beaker contains 300 g of water at #30^o C #. Water at #100^o C# is added until the temperature of the mixture reaches #50^o C#. The specific heat capacity of water is 4.2 J/#(g^o C)#. How much water is added?

Question

A 60 g
B 120 g
C 180 g
D 750 g

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Answer 1 · 2017-03-23T14:02:08

The answer is #B#

Let #(m)g# be the mass of water added.

The heat gained by the water at #30ºC=#the heat lost by the water at #100ºC#.

So,

#300*cancel4.2*(50-30)=m*cancel4.2(100-50)#

#300*20=m*50#

#m=300*20/50=120g#