A reaction occurs in a calorimeter that heats up 15g water from 25 oC to 50 oC. The specific heat of water is 4.184 J/goC. Determine the thermal energy (Q) that must have entered the water to produce this temperature change.

The thermal energy (Q) needed : = 1882.8 J

Given

15g water from 25 °C to 50 °C

Required

The thermal energy (Q)

Solution

Heat can be calculated using the formula:  

Q = mc∆T  

Q = heat, J  

m = mass, g  

c = specific heat, joules / g ° C  

∆T = temperature difference, ° C / K  

Input the value :

Q = 15 g x 4.184 J/g°C x (50 °C- 20 °C)

Q = 1882.8 J

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."