NEB Class 11 Science Chemistry Question Paper 2078

How many atoms are there in two molecules of water?

What is the number of moles of ammonia gas formed when 0.5 mole of nitrogen gas is reacted with excess of hydrogen gas?

Which of the following bonding is responsible for the solubility of ammonia gas in water?

What happens when Sulphur dioxide ($SO_2$) gas is passed through an acidified solution of hydrogen sulfide ($H_2S$) gas?

Which of the following property of crystalline substance describes the similar chemical composition?

$SO_3$ gas is formed as an intermediate during the manufacture of Sulphuric acid by contact process. The formation of Sulphur trioxide from sulfur dioxide and oxygen is reversible: $2SO_2+O_2 \rightleftharpoons 2SO_3,\ \Delta H=-196\ \text{kJ mol}^{-1}$. Which conditions of pressure and temperature favor the reverse reaction?

Which is the correct order of ease of carbon dioxide production by heating the Group II metal carbonates?

Which of the following is related to Batch process?

Sodium-glucose pump is an example of

An intermediate compound X is formed during the production of urea through ammonia/carbon dioxide technology. What is the molecular formula of X?

Which of the following are recycled in the manufacture of sodium Carbonate by Solvay's process?

An element X has 2 electrons in K shell, 8 electrons in L shell and 5 electrons in M shell.

i. Identify the element X and write the number of protons and electrons in it. $[3]$

ii. Size of $X^{3-}$ ion is greater than that of X atom though both contain the same number of protons. Give reason. $[1]$

iii. Write down the formula of one of the compounds of X where X is in $-3$ oxidation state. $[1]$

OR

Know-how about ionization energy (IE) of elements is crucial in the study of chemical bonding. The first ionization energies of period 2 elements are: Li 520, Be 899, B 801, C 1086, N 1403, O 1410, F 1681, Ne 2080 (kJ/mol).

i. Define first ionization energy. $[1]$

ii. Name a factor that affects the value of IE. $[1]$

iii. Which of the element is most difficult to ionize? $[1]$

iv. Why is there steep rise in IE from carbon to nitrogen? $[2]$

When electricity is passed through molten NaCl in the presence of CaCl₂ (ratio 2:3 by weight) using graphite anode and iron cathode, sodium metal is deposited at the cathode and chlorine gas is liberated at the anode.

i. Define electrolytic cell. $[1]$

ii. Find the mass of sodium metal deposited at cathode when 0.1 ampere of current is passed for half an hour and the process has 75% efficiency. $[2]$

iii. Why does calcium metal not deposit instead of sodium at the cathode? $[1]$

iv. Aqueous solution of sodium chloride cannot be used instead of molten sodium chloride for the same intended product. Give reason. $[1]$

Derive the relationship between $K_p$ and $K_c$. Give one example of chemical reaction where $K_p$ is greater than $K_c$. $[4+1]$

OR

Derive the ideal gas equation $PV=nRT$ where the symbols have their usual meaning. State two conditions under which behavior of real gas approaches that of an ideal gas. $[3+2]$

Concentrated sulphuric acid can be used in the laboratory to produce hydrogen chloride gas by reaction with solid sodium chloride.

i. Hydrogen iodide is not produced by the same method as for hydrogen chloride. Why? $[1]$

ii. What is the difference between hydrogen chloride gas and hydrochloric acid? $[2]$

iii. How could you identify the bottle containing HCl using ammonia gas? $[2]$

Depending upon the nature of minerals present in the ores, calcination and roasting are mainly used for the conversion of ores into their respective oxides.

i. What do you mean by roasting and calcination in the metallurgical process? $[2]$

ii. Name the vessel in which roasting is carried out. $[1]$

iii. Write the name of two possible impurities that are removed in roasting. $[2]$

An example of a homologous series is given below:

$CH_3OH$

$CH_3CH_2OH$

$X$

$CH_3CH_2CH_2CH_2OH$

i. Define homologous series. $[1]$

ii. Find the mass difference between successive members of the above homologous series and calculate the molecular mass of X. $[2]$

iii. What is the reason behind the highest boiling point but least solubility of the fourth member in the given series? $[2]$

An unsaturated hydrocarbon B upon treatment with Hydrogen bromide produces compound C. Compound C reacts with sodium metal in the presence of organic ether produces compound D of molecular formula $C_6H_{14}$.

i. Give the chemical equations for the conversion of compound B to compound C and compound C to compound D. $[2]$

ii. Write down the IUPAC name of compound C and D. $[2]$

iii. Give the structural formula of positional isomer of compound C. $[1]$

Urea is a much-demanded chemical fertilizer in an agricultural country like Nepal because of the lack of domestic production. One of the raw materials for urea production is ammonia which is obtained from Haber's process.

i. Draw a flow sheet diagram for the manufacture of Ammonia by Haber's-Bosch Process. $[3]$

ii. What is the major challenge in establishing chemical industries in countries like Nepal? Mention how such challenge can be strategically overcome. $[2]$

In the presence of platinum catalyst ammonia is oxidized to nitric oxide: $4NH_3+5O_2 \xrightarrow{Pt} 4NO+6H_2O$.

i. Calculate the mass of Nitric oxide produced by the reaction of 2 mole of ammonia with 2 moles of oxygen. $[2]$

ii. What is the importance of limiting reactant in chemical calculation? $[1]$

iii. If 2 moles of ammonia produce 50 grams of water upon reaction with excess of ammonia. What is the percentage yield of the reaction? $[2]$

iv. Calculate the volume of HCl gas required at $20^\circ C$ and 750 mm Hg pressure which can completely react with 2 mole of ammonia gas to produce ammonium chloride. $[3]$

Oxygen readily forms oxides with other elements. Some oxides are: $Na_2O,\ Al_2O_3,\ CO,\ SO_2,\ Fe_3O_4,\ H_2O_2$.

i. Identify the acidic oxide, basic oxide, neutral oxide and mixed oxide from the above table. $[4]$

ii. Write two chemical equations to prove that the particular oxide is amphoteric in nature. $[2]$

iii. Why is CO a harmful gas? $[1]$

iv. Write any one industrial application of oxygen gas. $[1]$

OR

Sulfuric acid is produced by the contact process.

i. Write the four-step chemical equations for the manufacture of sulphuric acid by contact process starting from iron sulfide. $[4]$

ii. Give any two chemical equations in which sulphuric acid acts as a precipitant and a dehydrating agent. $[2]$

iii. Write the chemical equation producing fertilizer using $H_2SO_4$. $[1]$

iv. Why does $H_2SO_4$ always act as an oxidizing agent? $[1]$

An alkene X undergoes ozonolysis and gives two compounds Y and Z of molecular formula $C_3H_6O$. Y and Z are functional isomers of each other.

i. Write the two-step chemical equation for the conversion of X into Y and Z. $[2]$

ii. Write the structural formula of Y and Z. Why are they called functional isomers? $[3]$

iii. What happens when hydrogen gas in the presence of nickel catalyst is passed over X? $[1]$

iv. What is the application of ozonolysis in the organic reaction mechanism? $[1]$

v. How can you prove chemically that the compound X is unsaturated? $[1]$