LACHATELIER\'S Principle Pre-lab questions; 1. show calculations and briefly des
ID: 712416 • Letter: L
Question
LACHATELIER'S Principle
Pre-lab questions;
1. show calculations and briefly describe how you will make the following solutions.
a. 50 ml of 0.200M Fe(NO3)3 (aq) solution from iron(III) nitrate nonhydrate
b. 200 ml of a 2.00 mM KSCN(aq) solution from potassium thiocynate
c. 100 ml of 1.00M CoCl2 (aq) solution from Cobalt (II) chloride hexahydrate.
2. Write equiblibrium expression for parts A, B and C of the lab based on the Equations that are shown in the prior section.
3. Look at the expression for the cobalt complexation with chloride ions. How would doubling the amount of water in the reaction vessel affect the product concentrations compared to the reactant concentration?
4. Many of the steps in this lab require that test tubes are transferred between boiling baths and ice baths. why is it important that these tubes are made of either Pyrex or Kimax glass?
Explanation / Answer
1)
a. no of moles of Fe(NO3)3 = molarity * volume in L
= 0.2*0.05 = 0.01 moles
mass of Fe(NO3)3 = no of moles * gram molar mass
= 0.01*241.86 = 2.42g
2.42g of Fe(NO3)2 disolve in 5oml of solution
b.
no of moles of KSCN = molarity * volume in L
= 2*10-3 *0.2 = 0.002*0.2 = 0.0004 moles
mass of KSCN = no of moles * gram molar mass
= 0.0004*97.18 = 0.039g
0.039g of KSCN disolve in 200ml of solution
c.
no of moles of COCl2 = molarity*volume in L
= 1*0.1 = 0.1 mole
mass of CoCl2 = no of moles * gram molar mass
= 0.1*98.92 = 9.892g
9.892g of CoCl2 disolve in 100ml of solution
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