A student dissolves 10.7 g of sodium chloride NaClin 300. g of water in a well-insulated open cup. He then observes the temperature of the water fall from 22.0 °C to 21.4 °C over the course of 8.5 minutes.Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction:→NaCls + Na+aq Cl−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 NaCl. kJmolCheckSave For LaterSubmit AssignmentTerms of Use
Question
A student dissolves 10.7 g of sodium chloride NaClin 300. g of water in a well-insulated open cup. He then observes the temperature of the water fall from 22.0 °C to 21.4 °C over the course of 8.5 minutes.Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction:→NaCls + Na+aq Cl−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 NaCl. kJmolCheckSave For LaterSubmit AssignmentTerms of Use
Solution
The reaction is endothermic. This is because the temperature of the water decreased when the sodium chloride was dissolved, indicating that heat was absorbed from the water by the reaction.
To calculate the amount of heat absorbed by the reaction, we first need to calculate the change in temperature in Kelvin. The change in temperature is 22.0 °C - 21.4 °C = 0.6 °C, which is equivalent to 0.6 K.
Next, we use the formula q = mcΔT, where q is the heat absorbed, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature. The specific heat capacity of water is approximately 4.18 J/g·K.
So, q = (300 g)(4.18 J/g·K)(0.6 K) = 753.6 J.
However, the question asks for the answer in kilojoules, so we need to convert joules to kilojoules by dividing by 1000.
So, q = 753.6 J / 1000 = 0.754 kJ (rounded to three decimal places).
To calculate the reaction enthalpy ΔHrxn per mole of NaCl, we first need to calculate the number of moles of NaCl. The molar mass of NaCl is approximately 58.44 g/mol.
So, the number of moles of NaCl = 10.7 g / 58.44 g/mol = 0.183 mol (rounded to three decimal places).
Finally, we calculate ΔHrxn = q / number of moles = 0.754 kJ / 0.183 mol = 4.12 kJ/mol (rounded to three decimal places).
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