Hi there, I just need help with these 3 Calorimetry questions. Please show your

Question

Hi there,

I just need help with these 3 Calorimetry questions. Please show your work when possible. Thank you.

The three questions are based on the enthalpy of NaOH solution:

50 mL distilled water is placed in a calorimeter. 2.00 g (0.05 mol) NaOH is weighed in a dry 50 mL beaker, which is then added to the water and stirred until dissolved. Once the highest temperature has been recorded, 50 mL 1.0 M HCl is added and the solution is rinsed in the sink.

Q1) In this experiment, which of the following are the surroundings? Choose all that apply.
Select all that are True.

1. Air in the lab
2. NaOH pellets
3. Water
4. Styrofoam cup calorimeter

Last Answers: TFFT, TFTT Both are wrong

Q2) If a reaction is carried out in the calorimeter and the temperature change increases the reaction is said to be:

A) Endothermic

B) Exothermic

Q3) If the following data is collected in Part A, what is the heat capacity of the calorimeter? Answer in J/Co

Q2) If a reaction is carried out in the calorimeter and the temperature change increases the reaction is said to be:

A) Endothermic

B) Exothermic

Q3) If the following data is collected in Part A, what is the heat capacity of the calorimeter? Answer in J/Co

Ti cool water 21.9      Ti warm water 62.4 Tf 37.4

Explanation / Answer

1) In a thermodynamic set up where we have to determine changes in heat energy

a) System : It is the whole set up including water, stayfoam cup, the reactants like NaOH or HCl

b) Surrouding: Any thing surrounding the system, here it is air

2) If temperature is increased it means there is evolution of heat from the reaction hence the reaction is exothermic

In endothermic reaction heat is absorbed by the system.

3) The heat evolved during the reaction will heat up the cold water and will also cause rise in temperature of calorimeter

The heat evolved = Heat of reaction

Heat absorbed by water = Mass of water X change in temperature x specific heat of water

Mass of water = volume of water X density of water = 100mL X 1g / mL = 100 grams

(i) Heat evolved by hot water = 100g X (62.4 - 37.4) X 4.184 J / g 0C

Heat evolved by water = 10460 Joules = Qh

(ii) Heat gained by cold water = 100 X (37.4 -21.9) X 4.184 J / g 0C = 6485.2 Joules = Qc

(iii) Heat gained by calorimeter = Heat capacity x change in temperature = Heat capacity X (37.4 -21.9) = Qcal

Qh = Qc + Qcal

10460 = 6485.2 + Heat capacity X 8.3

Heat capacity = 478.89 Joules / 0C

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