section date Pre-Laboratory Assignment 1. The use of microscale techniques does
ID: 1036938 • Letter: S
Question
section date Pre-Laboratory Assignment 1. The use of microscale techniques does not change the hazardous natures of the reagents we use. Brietly observe after adding concentrated HCI to the equlib describe the hazards associated with even smal rum mixture amounts of each of the following: concentrated HCI, (1) Describe the color change the student should Na0H solution, AgNO, solution, and solid NaSO, 2) Briefly explain your answer to (1) in terms of Le Châtelier's principle. 2. Briefly explain the following: (1) chemical equilibrium (3) Describe the color change the student should observe after adding solid sodum chromate (Na CrON to the mixture prepared in (1). Recall that Na CrO4 dis- solves in water and dissociates into Na" and CrO ions. (2) endothermic reaction (3) Le Chatelier's principle (4) Briefly explain your answer to (3) in terms of Le Châtelier's principle. 3. A student is studying the equilibrium represented by the equation Cro, laq, orange)3ou The mixture obtained by the student is yellow.Explanation / Answer
1. Chemical hazards of,
concentrated HCl : extremely toxic to skin and organs, irritant, causes severe burns.
NaOH solution : irritant, corrosive, extremely harmful if swallowed.
AgNO3 solution : extremely reactive with other combustible materials. Toxic if swallowed.
acid NaHSO4 : extremly toxic to skin and organs, acute toxicity effect to living beings.
2. explain,
Chemical equilibrium : when in a reaction, the rate of forward reaction and rate of backward reaction becomes a constant and does not change, represented as Kc = products concentration/reactant concentration.
Exothermic reaction : reactions which gives off heat as part of products. enthalpy change is -ve.
LeChatellier's principle : If a change occurs in a chemical reaction at equilibrium, the direction of the reaction shifts to that side so as to minimize that change and reestablish equilibrium state again.
3. For the reaction,
chromate to dichromate
(1) yellow chromate changes to orange dichromate after addition of HCl.
(2) HCl added, excess H+ from HCl on the left hand side pushed the reaction towards the right hand side until all of added H+ is consumed and equilibrium is reestablished again.
(3) sodium chromate again a reactant, when added, the excess reactant pushed the reaction to the product side and more product is formed. The reaction becomes more orange.
(4) Excess chromate would react with any H+ in solution to product dichromate and it will continue until all of excess chromate is consumed and equilibrium is reestablished again.
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