Question

A student dissolves 14.8 g of ammonium nitrate (NH4NO2) in 300. g of water in a well-insulated open cup. He then observes the temperature of the water fall from 20.0°C to 15.0°C over the course of 4.3 minutes. Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction:
NH4NO3(s) → NH4+(aq) + NO3^- (aq)

Required:
a. Is this reaction exothermic, endothermic, or neither?
b. 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.

Answer 1

Answer:

a. Endothermic

b. 6586J are absorbed.

Explanation:

a. When the reaction occurs, the temperature is decreasing from 20.0°C to 15.0°C, that means the reaction is absorbing heat and is endothermic.

b. To find the heat absorbed we must use:

Q = -m*ΔT*C

Where Q is change in heat,

m is the mass of solution (300g + 14.8g = 314.8g)

ΔT is change in temperature (15.0°C - 20.0° = -5.0°C)

And C is specific heat of the solution (4.184J/g°C assuming is the same heat than the heat of pure water).

Replacing:

Q = -314.8g*-5.0°C*4.184J/g°C

Q =

6586J are absorbed