A50.0 g sample of liquid water cools a total of 68 °c. how much energy is involved in this change

The energy involved is -14,000 J or -14 kJ.

The specific heat for water is 4.184 J/g • °C. We know the mass of the water as 50.0 grams, and the phrase "..water cools a total of 68°C." means the temperature changed 68°C. (in this case the sign would be negative as the temperature cooled). So the energy involved is:

q= msΔT=(50.0g)(14.184J/g. °c) (-68°c)= -14.000J <or> 14kJ

Explanation:The field of thermochemistry (and thermodynamics) deals with the changes in heat and energy in chemical systems for both chemical reactions and physical processes involving chemicals. Different characteristic thermodynamic parameters have developed over time with two of them being specific heat (sometimes called specific heat capacity) and the other heat capacity. Specific heat, s, (or specific heat capacity, CP) is a measure of the quantity of heat required to change the temperature of a substance by one degree Celsius (or Kelvin). This gives it typical units of J/g • °C. The equation for the heat (or energy) for a change in temperature for a substance is:

q=msΔT<or>q=mCpΔT

where q is the amount of energy or heat changing, m is the mass of the substance in grams, s is the specific heat (CP is specific heat capacity) for the substance, and T is temperature (ΔT is the temperature change)/Heat capacity, C, on the other hand is the heat required to raise the temperature one degree Celsius (or Kelvin) for a given quantity of a substance (units J/°C. For example, the specific heat for pure copper metal is 0.385 J/g • °C whereas the heat capacity for 50 grams of copper is 50gx0.385J/g•°C=19.3J/°C. The equation for it is:C=ms

where C is the heat capacity with m and s defined above.