Question

A student dissolves 15.0 g of ammonium chloride (NH,CI) in 250. g of water in a well-insulated open cup. She then observes the temperature of the water fall from 20.0°C to 16.0 °C over the course of 5.3 minutes. Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction: NHCl(s) + NH(aq) + Cl (aq) You can make any reasonable assumptions about the physical properties of the solution. Be sure answers you calculate using measured data are rounded to the correct number of 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. exothermic Is this reaction exothermic, endothermic, or neither? endothermic X ó ? neither If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case. Calculate the reaction enthalpy AH x per mole of NHACI. 'mol

Answer 1

1) since temperature is drop during reaction it means heat is absorbed in reaction so it is endothermic reaction.

2) mass of solution = 15 + 250 = 265 gm

Let specific heat of solution is 4.2 J / gm C

( Assumed solution is extremely diluted)

Heat absorbed = ( 265 gm ) x ( 4.2 J / gm^{​​​​​0} C ) x 4  ⁰C = 4452 J

Ans is 4.45 KJ

3) moles of NH4Cl = 15 gm / 53.49 gm mol--1 = 0.28 mol

Since 0.28 mol absorbed heat = 4.45 KJ

So heat absorbed by 1 mol = 4.45 KJ / 0.28 mol = 15.9 KJ / mol