NEB Class 12 Science Chemistry (Technical Stream) Question Paper 2082

Which of the following indicator is suitable for the titration between ethanoic acid and NaOH?

The enthalpy change for the reaction;

is $-93.7\,\text{KJmol}^{-1}$, what kind of reaction is it?

Which of the following species can act both as Bronsted acid and Bronsted base?

When copper is heated in air at above $1100\,^0C$, which of the following compounds is formed?

For which manufacturing process, Bessemer converter is used?

The substance 'A' which reacts with gangue to form fusible mass. The substance 'A' is called

An organic compound (A) boiled with water gives phenol. Predict the compound (A).

Which of the following compounds cannot reduce Fehling's solution?

Which of the following methods can you apply to convert rectified spirit into absolute alcohol?

Identify the compound (A)?

Which of the following drugs is used to reduce body temperature during high fever?

The fundamental principle of titration is based on the law of chemical equivalence.

a) What does it mean?

b) Derive normality equation using the law of equivalence.

c) 10cc of N/2 HCl, 30cc of N/10 $HNO_3$ and 60cc of N/5 $H_2SO_4$ are mixed. Calculate the normality of the mixture.

Or

State and explain first law of thermodynamics. Give the name of any two home appliances that work on the principle of $1^{st}$ law of thermodynamics. $[3+2]$

Acidic strength of solution can be measured in term of pH value.

a) Define pH of a solution.

b) What is the application of pH in our daily life?

c) What is pOH and how is it related to pH?

d) Calculate the pH of $5\times10^{-4}$ M $H_2SO_4$ solution.

Derive and explain integrated rate equation and half life for a zero order reaction.

Standard hydrogen electrode can be used as reference electrode.

a) Define standard hydrogen electrode.

b) What is the major application of standard hydrogen electrode?

c) Draw well labeled diagram of standard hydrogen electrode.

d) What is meant by standard electrode potential?

Derive the equation $\Delta G = \Delta H - T\Delta S$. Why useful work of system is called free energy? $[4+1]$

Differentiate between:

a) Calcination and roasting

b) Froth floatation and magnetic separation process.

Write down the functional isomer of $C_3H_6O$ with their IUPAC names. How are they distinguished by Tollen's reagent? How would you obtain these isomers by dehydrogenation of alcohols? $[2+1+2]$

Write an example of each of the following reactions: $[1+1+1+1+1]$

a) Dow's process

b) Wurtz reaction

c) 2, 4- DNP test

d) Preparation of alcohol from ester.

e) Preparation of phenol from benzene sulphonic acid

Or

The vapour of organic compound (A), if inhaled causes the loss of consciousness and if heated with conc.$HNO_3$ forms a component of tear gas.

i) How would you prepare compound (A) by using one of the isomers of $C_2H_6O$. $[2]$

ii) What happens when compound (A) is: $[1+1+1]$

a) exposed in air

b) heated with Ag powder

c) heated with aqueous alkali

Define the rate of chemical reaction. How do concentration, temperature, catalyst and surface area of reactants affect the rate of reaction? The half life period of first order reaction is 3 hours. Calculate the time required to complete 87.5% of the reaction. $[1+4+3]$

Or

Differentiate between solubility and solubility product. How is solubility product principle helpful in the qualitative salt analysis? $[2+6]$

Iron is a heavy metal and extracted from its oxide ore.

a) Write the name of any two ores of iron.

b) Draw the clean and labelled diagram of the blast furnace showing different zones.

c) Write the reactions involved in different zones.

d) Mention the application of iron in our daily life.

Or

Explain the principle and process sketching a well labelled diagram for the extraction of zinc from its ore. What happen when zinc is exposed to moist air? $[6+2]$

a) Radioactivity was discovered accidentally by a scientist Henry Becquerel (1896).

i) What is radioactivity? Write its unit.

ii) What is meant by artificial radioactivity? Write an example of it.

b) Mention one example and use of each of the following: $[4]$

i) Insecticide

ii) Synthetic polymer

iii) Antiseptic

iv) Fungicide