P\'re-Laboratory Assignment 1. The use of microscale techniques does not change
ID: 1084947 • Letter: P
Question
P're-Laboratory Assignment 1. The use of microscale techniques does not change the hazardous natures of the reagents we Briefly describe the hazards associated with even small amounts of each of the following concentrated HCI, NaOH solution, AgNO, solution, and solid NaHSO4 use. 2. Briefly explain the following (1) chemical equilibrium (2) endothermic reaction (3) Le Châtelier's principle 3. A student is studying the equilibrium represented by the equation 2CrO, (aq yellow) +2H,O (ag) Cr,O, (ag, orange) +3H,00) The mixture obtained by the student is yellow. (1) Describe the color change the student should observe after adding concentrated HCI to the equilibrium mixture. (2) Briefly explain your answer to (1) in terms of Le Châtelier's principle.Explanation / Answer
Answer 1) Hazardous nature of Reagents
(i) Hydrochloric acid is a hazardous liquid which must be used with care. The acid itself is corrosive, and concentrated forms release acidic mists that are also dangerous. If the acid or mist come into contact with the skin, eyes, or internal organs, the damage can be irreversible or even fatal in severe cases. The use of personal protective equipment is essential.
(ii) NaOH Solution,the substance is a strong base, it reacts violently with acid and is corrosive in moist air to metals like zinc, aluminium, tin and lead forming a combustible/explosive gas . Reacts with ammonium salts to produce ammonia , causing fire hazard. Rapidly absorbs carbon dioxide and water from air. Contact with moisture or water may generate heat. The substance is very corrosive to the eyes, the skin and the respiratory tract. Corrosive on ingestion. Inhalation of an aerosol of the substance may cause lung oedema
(iii) AgNO3 solution, The substance decomposes on heating producing toxic fumes including nitrogen oxides . The substance is a strong oxidant and reacts violently with combustible and reducing materials. Reacts with incompatible substances such as acetylene, alkalies, halides and many other compounds causing fire and explosion hazard.
(iv) Solid NaHSO4, Very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (corrosive, permeator). The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastrointestinal or respiratory tract, characterized by burning, sneezing and coughing
Answer (2)
(a) In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time.[1] Usually, this state results when the forward reaction proceeds at the same rate as the reverse reaction.
(b) The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings; usually, but not always, in the form of heat.
(c) Le Chatelier's principle, also called Chatelier's principle or "The Equilibrium Law", can be used to predict the effect of a change in conditions on a chemical equilibrium. When any system at equilibrium is subjected to change in concentration, temperature, volume, or pressure, then the system readjusts itself to counteract (partially) the effect of the applied change and a new equilibrium is established. In other words, whenever a system in equilibrium is disturbed the system will adjust itself in such a way that the effect of the change will be nullified.
Answer (3)
(1) The colour of final mixture is orange. the colour of mixture is changes to yellow to orange after adding hcl in the mixture
(2) According to Le Chatelier's principle whenever a system in equilibrium is disturbed the system will adjust itself in such a way that the effect of the change will be nullified.
after adding HCl in the mixture reaction moves forword and the more Cr2O72- is formed and colour of solution turns orange colour
(3) The colour of final mixture is orange. the colour of mixture is changes to yellow to orange after adding CrO42- in the mixture
(4) According to Le Chatelier's principle whenever a system in equilibrium is disturbed the system will adjust itself in such a way that the effect of the change will be nullified.
after adding CrO42- in the mixture reaction moves forword and the more Cr2O72- is formed and colour of solution turns orange colour
(5) The colour of final mixture is yellow. the colour of mixture is changes to yellow to orange after adding NaOH in the mixture
(6) Net ionic equation
2CrO42- + 2H+ H2O + Cr2O72- (initial reaction )
Cr2O72- + 2OH- H2O + 2CrO42- (After adding NaOH)
(7) after adding NaOH in the mixture reaction moves backward as the naoh solution nutralizes the h+ concountraion of the reation and reaction moves in backward direction so colour of solution mixture is yellow
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