Astudent dissolves of potassium chloride in of water in a well-insulated open cup. he then observes the temperature of the water fall from to over the course of minutes. use this data, and any information you need from the aleks data resource, to answer the questions below about this reaction: you can make any reasonable assumptions about the physical properties of the solution. be sure answers you calculate using measured data are rounded to 2 significant digits. note for advanced students: it's possible the student did not do the experiment carefully, and the values you calculate may not be the same as the known and published values for this reaction. is this reaction exothermic, endothermic, or neither. calculate the reaction enthalpy aw per mole of naoh

1) Endothermic

2) Heat absorbed by reaction = 2511.6J

3)ΔH_rxn = 18.2 kJ/ mol

Explanation:

Mass of KCl = 10.3 g

Moles of KCl = mass of KCl / molar mass of KCl

= 10.3 g / 74.5513 g/mol

=0.138 mol

Mass of water, m = 200 g

Specific heat of water, C= 4.186 Jg^-1°C^-1

T_initial = 22.0C

T_final = 19.0°C

ΔT = T_final - T_initial

=19.0°C - 22.0°C

= -3.0°C

Heat absorbed = Heat released

q_rxn =-q_water

so,

q_water = m CΔT

substitute

q_water = 200g * 4.186J g^-1 °C^-1 *(-3.0°C)

= -2511.6J

Heat absorbed by reaction = 2511.6J

q_rxn = -q_water = 2511.6J

ΔH_rxn = q_rxn /moles of KCl

=2511.6J / 0.138 mol

ΔH_rxn =18.2kJ / mol

The reaction is a endothermic reaction.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.