2. how many grams of water can be heated from 20.0°c to 75°c using

12500.0 joules?

Grams of water can be heated from 20.0°C to 75°C using  12500.0 Joules = 54.3 g

Explanation:

Heat required to increase temperature

                 H = mcΔT

m = mass of material

C = specific heat of material

ΔT = Change in temperature.

Here we need to find  how many grams of water can be heated from 20.0°C to 75°C using  12500.0 Joules

That is

            H = 12500 J

            Specific heat of water, C = 4186 J/kg°C

            ΔT = 75 - 20 = 55

Substituting

            12500 = m x 4186 x 55

              m = 0.0543 kg

              m = 54.3 g

Grams of water can be heated from 20.0°C to 75°C using  12500.0 Joules = 54.3 g

pythagoras' theorem

square root (-5^2+9^2)

square root (25+81)

square root (106)

angle is tan^-1(9/5)

neg x, pos y