A student dissolves 11.6 g of sodium hydroxide NaOHin 300. g of water in a well-insulated open cup. He then observes the temperature of the water rise from 23.0 °C to 33.9 °C over the course of 6.1 minutes.Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction:→NaOHs + Na+aq OH−aqYou 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.Is this reaction exothermic, endothermic, or neither? exothermicendothermicneitherIf you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case. kJCalculate the reaction enthalpy ΔHrxn per mole of NaOH. kJmol
Question
A student dissolves 11.6 g of sodium hydroxide NaOHin 300. g of water in a well-insulated open cup. He then observes the temperature of the water rise from 23.0 °C to 33.9 °C over the course of 6.1 minutes.Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction:→NaOHs + Na+aq OH−aqYou 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.Is this reaction exothermic, endothermic, or neither? exothermicendothermicneitherIf you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case. kJCalculate the reaction enthalpy ΔHrxn per mole of NaOH. kJmol
Solution
This reaction is exothermic. An exothermic reaction is one in which heat is released. This is evident from the increase in temperature of the water.
To calculate the amount of heat released, we can use the formula q = mcΔT, where m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.
Given: m = 300 g c = 4.18 J/g°C (specific heat capacity of water) ΔT = 33.9°C - 23.0°C = 10.9°C
Substituting these values into the formula, we get:
q = (300 g)(4.18 J/g°C)(10.9°C) = 13662 J
Since 1 kJ = 1000 J, we convert the heat to kJ:
q = 13662 J ÷ 1000 = 13.662 kJ
So, the amount of heat released by the reaction is approximately 13.7 kJ (rounded to the correct number of significant digits).
To calculate the reaction enthalpy ΔHrxn per mole of NaOH, we first need to find the number of moles of NaOH. We can do this using the formula n = m/M, where m is the mass of the NaOH and M is the molar mass of NaOH.
Given: m = 11.6 g M = 40.00 g/mol (molar mass of NaOH)
Substituting these values into the formula, we get:
n = 11.6 g ÷ 40.00 g/mol = 0.29 mol
Finally, we can calculate ΔHrxn by dividing the heat released by the number of moles:
ΔHrxn = q/n = 13.7 kJ ÷ 0.29 mol = 47.24 kJ/mol
So, the reaction enthalpy ΔHrxn per mole of NaOH is approximately 47.2 kJ/mol (rounded to the correct number of significant digits).
Similar Questions
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