HSC Chemistry paper board Solution 2020 of class 12 with complete explanation
HSC Board Chemistry Question paper 2020 Click to refer
Important Questions for Chemistry Old Syllabus Repeater students 2020 Click to refer
Select and write the correct answer of the following : – [10M]
- Identify synthetic polymer amongst the following :
- Terylene (Correct answer)
- Which among the following hydrides is NOT a reducing agent?
- H2O (Correct Answer)
- During oxidation of ferrous sulphate using mixture of dil. H2SO4 and potassium dichromate ; oxidation state of chromium changes from __________
- +6 to +2
- +6 to +3 (Correct Answer)
- +6 to +1
- +6 to +4
- Identify complex ion in which effective atomic number of the central metal ion is 35.(Given At. number of Co=27,Fe=26,Zn=30)
- [Fe(CN6)]3- (Correct Answer)
- Conversion of methyl chloride into methyl fluoride is known as _________
- Finkelstein reaction
- Swartz reaction (Correct Answer)
- Willianson’s Synthesis
- Wurtz Reaction
- The number of moles of methyl iodide required to prepare tetramethyl ammonium iodide from 1 mole of methyl amine is/are:
- 3 (Correct Answer)
- Name the reagent which on reaction with glucose confirms the presence of five hydroxyl groups in glucose:
- Hydroxyl Amine
- Bromine water
- Dilute nitric acid
- Acetic anhydride (Correct Answer)
- Identify antibiotic drug amongst the following:
- Penicillin (Correct answer)
- The Number of atoms per unit cell of body centred cube is:
- 2 (Correct answer)
- Calculate the work done during the reaction represented by the following thermodynamic equation at 300k: CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)….(where g is for gas and l for liquid)
- +4.988kJ (Correct Answer)
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Q.2) Answer the Following questions: — [8M]
a). What is the Concentration of dissolved oxygen at 500C under pressure of one atmospheric if partial pressure of oxygen at 500C is 0.14 atm. (Henry’s law constant for oxygen = 1.3 * 10-3 mol dm–3 atm -1)
Answer: 1.82 × 10-4 mol dm-3.
b). Write the Structural formulae of the alcohol that results when acetaldehyde is reacted with CH3MgBr in the presence of dry ether and the product is hydrolysed?
Answer: isopropyl alcohol/2-hydroxypropane
c). Write balanced chemical reaction for preparation of acetic anhydride using acetic acid ?
d). Write the chemical reaction involved in the formation of ethyl amine using acetal doxime.
e). What is electrometallurgy?
Answer: Electrometallurgy is a method that uses electrical energy goes into electrolytic reduction of molten(fused) metallic compounds to produce metals.
SECTION – B (HSC Chemistry Board Paper Solution 2020)
Q3. State and explain Hess’s law of constant heat summation.
Answer: The law states that the change in enthalpy for a reaction is the same whether the raction takes place in one or
series of steps./ The enthalpy change for a chemical reaction is the same regardless of the path by which reaction occurs.
The conversion of A ->C can directly takes place in one step
A –> C ΔH0 = ΔH1
The reaction can also takes place in two different steps
Step 1 A -> B ΔH0 = ΔH2
Step 2 B -> C ΔH0 = ΔH3
Overall A -> C ΔH0 = ΔH2 + ΔH
Q5). Distinguish between order and molecularity of a reaction.
|It is the sum of powers of the concentrations in the rate law expressions||It is the number of molecules of the reactants taking part in elementary reaction.|
|It is an experimentally determined value.||It is a theoretical concept.|
|Order corresponds to the overall reaction.||Molecularity is for elementary reaction.|
|It can have fractional value.||It is always a whole number.|
Q6). Write two uses of each of the follwing
Answer: Uses of Helium-
i) It is used for filling balloons and air ships as it is light and non combustible.
ii) It is used in producing inert in metallurgical operations and welding of metals.
i) It is also used in television sets, spark plug, warning signals etc.
ii) It is also used in safety devices, electrical instruments like voltage stabilizer and rectifier’s
Q7). Write the name and chemical formulae of one ore of zinc.? Define Quaternary ammonium salt.
Answer: Zinc belnde ZnS, calamine ZnCO3, Zincite ZnO, willemite ZnSO4.
Tetraalkylammonium halide are called quaternary ammonium salt.
The property or phenomenon of certain organic substances to rotate the plane of plane polarized light towards right(clockwise) or left(anti-clockwise) through certain angle is called optical activity.
Number of optical isomer of glucose is 24 = 16. As glucose has 4 asymmetric carbon atom.
As per the reaction above
Sulphuric acid regenerated in the second step is reused in the first step. Thus the small amount of sulphuric acid converts a large amount of ethyl alcohol into diethyl ether and the process becomes continuous. Hence it is called a continuous etherification process.
Hormones are chemicals released by the endocrine glands to control and regulate the activity of certain cells
. Silver- Metallic solid
P4 –Molecular solid
Diamond-Covalent solid ,
NaCl – Ionic solid
Molality-The number of moles of solute dissolved in 1 kg of a solvent is known as molarity.
Osmotic pressure- The excess of pressure on the side of the solution that stops the net flow of solvent into solution through a semipermeable membrane is called osmotic pressure.
SECTION – C
Attempt any eight questions of the following-
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