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Answer parts (a)-(e) in Section II Answer Booklet 1 - HSC - SSCE Chemistry - Question 32 - 2060 - Paper 1
Question 32
Answer parts (a)-(e) in Section II Answer Booklet 1. (a) This diagram illustrates some of the properties of sulfuric acid. Drop of concentrated H2SO4 Drop of dilu... show full transcript
Worked Solution & Example Answer:Answer parts (a)-(e) in Section II Answer Booklet 1 - HSC - SSCE Chemistry - Question 32 - 2060 - Paper 1
Step 1
Explain, with reference to the diagram, how sulfuric acid should be transported.
Answer
The diagram depicts different interactions of concentrated and dilute sulfuric acid with both steel and glass surfaces.
When concentrated sulfuric acid is applied to steel, there is no bubbling because the reaction is minimal. However, the use of concentrated sulfuric acid should be approached with caution as it can corrode steel surfaces over time, leading to structural damage. In contrast, when dilute sulfuric acid is introduced, there is vigorous bubbling, indicating a reaction that produces gas.
On the glass surface, both concentrated and dilute acids cause no bubbling, suggesting no significant reaction occurs. This highlights that sulfuric acid should be transported in a glass container to prevent corrosion and reaction with the container material while avoiding vigorous reactions.
Step 2
Explain the effect on the yield of NO(g) if the temperature is increased.
Answer
According to Le Chatelier’s principle, increasing the temperature of an endothermic reaction will shift the equilibrium to favor the formation of products. Hence, raising the temperature will increase the yield of NO(g) as the system seeks to absorb the added heat by favoring the forward reaction.
Step 3
Calculate the equilibrium concentration of NOCl(g) if the equilibrium concentration of Cl2(g) is 0.17 mol L–1.
Answer
The reaction is given by:
Using the equilibrium constant, K:
K = rac{[NO]^2 [Cl_2]}{[NOCl]^2} = 0.028
Let [Cl2] = 0.17 mol L–1 and let [NO] = x, then:
K = rac{(x^2)(0.17)}{([NOCl])^2} = 0.028
We will first solve for [NO]:
Assuming total moles react and hence,
Then,
0.028 = rac{(0.34^2)(0.17)}{[NOCl]^2}
This gives us:
Thus, solving for [NOCl]:
.
Step 4
Contrast the energy transformations in galvanic and electrolytic cells.
Answer
In galvanic cells, chemical energy is converted into electrical energy during spontaneous reactions. This process harnesses the energy released from the reaction to generate electrical power.
Conversely, electrolytic cells require an external source of electrical energy to drive non-spontaneous reactions. Here, electrical energy is converted into chemical energy as it induces chemical processes to occur.
Step 5
Explain which of the three electrolytic cells from the table is used for the industrial production of sodium hydroxide.
Answer
Electrolytic cell Z is used for the industrial production of sodium hydroxide. In this cell, Cl2(g) is produced at the anode, and Na(l) is produced at the cathode. The electrolysis of sodium chloride solution (brine) yields sodium hydroxide along with hydrogen and chlorine. The presence of sodium at the cathode indicates the production of NaOH in this cell.
Step 6
Outline a valid procedure that could be used to carry out the investigation.
Answer
To carry out an investigation for the Solvay process, dissolve a measured amount of NaHCO3 into a test tube, ensuring the test tube is held at an angle. Use a delivery tube fitted with a stopper at the mouth of the test tube. Immerse the other end of the delivery tube into a second container filled with water. Apply heat to the water bath while monitoring the reaction carefully at the NaHCO3 until gaseous evolution can be observed.
Step 7
Describe TWO limitations associated with the procedure outlined in part (i).
Answer
Firstly, one limitation is that the reaction is influenced by external factors such as temperature and pressure, which can vary during the experiment. This may lead to inconsistent results.
Secondly, the modelling may not encompass all variables involved in the actual Solvay process, thereby limiting the validity of the findings to the broader industrial context.
Step 8
Explain how the differences in the structure and composition of soaps and detergents determine their uses and their impacts on the environment.
Answer
Soaps possess a long non-polar hydrocarbon chain along with a polar carboxylate end, allowing them to effectively emulsify oils and grease in water. This structure makes them suitable for cleaning purposes but can lead to environmental pollution if they enter natural water bodies.
Detergents, while still effective in cleaning, have variations in their chemical composition that allow for greater efficacy in hard water. However, some types of detergents may contain phosphates, which can contribute to eutrophication in water bodies. Therefore, both soaps and detergents have their designated applications influenced by their structural composition, coupled with potential negative environmental impacts.