What is/are the purpose(s) of the Styrofoam cups in this experiment? What are so

Question

What is/are the purpose(s) of the Styrofoam cups in this experiment? What are some assumptions that we make during this experiment in order to calculate the enthalpy of formation of ammonium sulfate? Calculate the mass of the solution used if a student added 35.369 grams of ammonium sulfate to enough water to give 80.0 mL of solution. The density of the solution was 1.00 g/mL. How many significant figures should your answer have? For the reaction (i.e., Part I of this experiment, calculate the number of moles of the limiting reactant when 25.0 mL of 2.085 M H_2SO_4 (aq) it mixed with 50.0 mL of 1.873 M NH_3(aq) using the molar ratio of the reaction. Show your work with the correct units and number of significant figures

Explanation / Answer

1. Styroform cup is used to ensure proper insulation of heat.

2. Assumptions : (a) heat liberate = heat absorbed and no heat loss to the environ ment (b) reactants react completely.

3.80mL solution = 80mL water = 80 gm

mass of solution used = 80gm

4. 2NH3 + H2SO4 ==> (NH4)2SO4

moles of H2SO4 used =25mL*2.085 M/1000mL =0.052 moles

Moles of NH3 used = 50mL*1.873M/1000mL = 0.094 moles

2 moles NH3 reacts with 1 mole H2SO4. Moles of NH3 required to react with 0.052 moles of H2SO4 = 0.052*2 =0.104 moles.

So, the limiting reagent is NH3 as it will be completely consumed.

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