how to measure mass without Q?

a 100°C hot water is added to a 300g of water with initial temperature of 0°C until it reaches 40°C.

what is the initial mass of the added hot water?

2 Answers

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  • Vaman
    Lv 7
    5 months ago

    300gm water needs energy= 40 s *300. This must be given by

    (100-40) s mass of hot water. mass of hot water= 1200/60=200 gm This is the answer given below. s is called a the specific heat of water.

  • 5 months ago

    energy required to warm the 300 g of water:

    E = 4.186 J/gC x 300 x (40–0) = 50232 J

    that must equal energy to cool the added mass

    E = 50232 J = 4.186 J/gC x M x (100–40) 

    M = 200 g

    actually the 4.186 J/gC terms cancel and you can use a symbol instead.

    E = SH x 300 x 40 = 12000•SH

    M = 12000•SH / 60•SH = 200 g

    specific heat of water is 4.186 kJ/kgC = 4.186 J/gC

       = 1 calorie/gC = 5.375 J/mol·K = 1 Btu/lb-F

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