Important Questions for CBSE Class 11 Chemistry Chapter 10 – The s-Block Elements

Important Questions Class 11 Chemistry Chapter 10 – The s-Block Elements

Chemistry is a subject based on theories, numerical, experiments, laws, principles, observations and conclusions. As a result, the subject is quite vast, and thus experts suggest students to revise the subject again and again with suitable study material hence parents and teachers trust Class 11 Chemistry Chapter 10 s block elements important questions to the fullest.

The s-Block elements are on the periodic table’s upper left-hand side. It is one of the smallest blocks of the periodic table. It comprises two groups. The main topics covered in the Chapter 10 Class 11 Chemistry S-block elements important questions include

• Group 1 element: alkali metals, 
• General characteristics of the compounds of the alkali metals, 
• Anomalous properties of Lithium, 
• Some important compounds of sodium, 
• Biological importance of sodium and potassium, 
• Group 2 elements: alkaline earth metals, 
• General characteristics of compounds of the alkaline earth metals, 
• Anomalous behaviour of beryllium, 
• Some important compounds of calcium,   
• Biological importance of magnesium and calcium.

You can find the detailed coverage of this chapter in the Important Questions Class 11 Chemistry Chapter 10 available on the Extramarks’ website. It is designed after analysing the mindset of different groups of students, and thus students find it easy to cope after studying it.

Extramarks is gaining praise and appreciation constantly due to its relentless service in the field of academics. Students can get NCERT solutions, NCERT textbooks, NCERT Exemplar, NCERT-based mock tests, NCERT revision notes and many more on the official website.

Get Access to CBSE Class 11 Chemistry Important Questions 2022-23 with Solutions

Sign Up and get complete access to CBSE Class 11 Chemistry Important Questions for other chapters too:

S block Elements Class 11 Important Questions with Answers

Below are a few Class 11 Chemistry Chapter 10 Important Questions and their solutions:

Question 1. The alkali metals have a low melting point. Which among the following alkali metal is expected to melt when the room temperature rises to 30°C?

(i) Na

(ii) K

(iii) Rb

(iv) Cs

Answer 1. (iv) Cs

 Option (iv) is the correct answer.

Question 2. Alkali metals react with the water vigorously to form the hydroxides and dihydrogen.

Which among the following alkali metals reacts with the water least vigorously?

(i) Li

(ii) Na

(iii) K

(iv) Cs

Answer 2. (i) Li

Option (i) is the answer.

Question 3. The reducing power of the metal depends on the different factors. Suggest the factor that makes Li one of the strongest reducing agents in the aqueous solution.

(i) Sublimation enthalpy

(ii) Ionisation enthalpy

(iii) Hydration enthalpy

(iv) Electron-gain enthalpy

Answer 3. (iii) Hydration enthalpy

Option (iii) is the answer.

Question 4. The metal carbonates decompose on heating to give the metal oxide and carbon dioxide. Which among the metal carbonates is the most stable thermally?

(i) MgCO3

(ii) CaCO3

(iii) SrCO3

(iv) BaCO3

Answer 4. (iv) BaCO3

Option (iv) is the answer.

Question 5. Which among the following carbonates given is unstable in air and is kept with the CO2 atmosphere to avoid the decomposition.

(i) BeCO3

(ii) MgCO3

(iii) CaCO3

(iv) BaCO3

Answer 5. (i) BeCO3

Option (i) is the answer.

Question 6. Metals form the basic hydroxides. Which among the following metal hydroxide is the least basic?

(i) Mg(OH)2

(ii) Ca(OH)2

(iii) Sr(OH)2

(iv) Ba(OH)2

Answer 6. (i) Mg(OH)2

Option (i) is the answer

Question 7. Some among the Group 2 metal halides are covalent and soluble in the organic solvents.

From the following metal halides, the one that is soluble in the ethanol is

(i) BeCl2

(ii) MgCl2

(iii) CaCl2

(iv) SrCl2

Answer 7. (i) BeCl2

Option (i) is the answer.

Question 8. The order for the decreasing ionization enthalpy in the alkali metals is

(i) Na > Li > K > Rb

(ii) Rb < Na < K < Li

(iii) Li > Na > K > Rb

(iv) K < Li < Na < Rb

Answer 8. (iii) Li > Na > K > Rb

Option (iii) is the answer.

Question 9. The solubility for the metal halides depends on their nature, the lattice enthalpy and the hydration enthalpy of the individual ions. From the following fluorides of the alkali metals, the lowest solubility of the LiF in water is because of the

(i) Ionic nature of lithium fluoride

(ii) High lattice enthalpy

(iii) High hydration enthalpy for lithium-ion.

(iv) Low ionization enthalpy of the lithium atom

Answer 9. (ii) High lattice enthalpy

Option (ii) is the answer.

Question 10. The amphoteric hydroxides react with both the alkalies and acids. Which among the

following Group 2, metal hydroxides are soluble in the sodium hydroxide?

(i) Be(OH)2

(ii) Mg(OH)2

(iii) Ca(OH)2

(iv) Ba(OH)2

Answer 10. (i) Be(OH)2

Option (i) is the answer.

 Question 11. Match the elements correctly given in Column I with their suitable properties mentioned in Column II.

Answer 11.

(i) is c

(ii) is b

(iii) is d

(iv) is a,e

Question 12. Match the compounds correctly given in Column I with their right uses mentioned in Column II.

Answer 12.

(i) is c

(ii) is d

(iii) is b

(iv) is a

Question 13. Match the elements correctly given in Column I with the appropriate colours they impart for the flame has given in Column II.

Answer 13.

(i) is f

(ii) is d

(iii) is b

(iv) is c

(v) is e

(vi) is a

Question 14. For the following questions, a statement of the Assertion (A) is followed by the statement of the Reason (R). Pick the correct option out of the alternatives given below each question.

(I). Assertion (A): The carbonate of the Lithium decomposes easily on heating to form the lithium oxide and CO2.

Reason (R): Lithium being very small in size polarises large carbonate ions leading to the formation of the more stable Li2O and CO2.

(i) Both of them, A and R, are correct, and R is the correct explanation for A.

(ii) Both of them, A and R, are correct, but R is not the correct explanation for A.

(iii) Both of them A and R are not correct

(iv) A is not right, but R is correct.

Answer (I). Option (i) is correct.

(II). Assertion (A): Beryllium carbonate is kept in the atmosphere of the carbon dioxide.

Reason (R): Beryllium carbonate is unstable as well as decomposes to give beryllium oxide and the carbon dioxide.

(i) Both of them, A and R, are correct, and R is the correct explanation for A.

(ii) Both of them, A and R, are correct, but R is not the correct explanation for A.

(iii) Both of them, A and R, are not correct.

(iv) A is not correct, but R is right.

Answer (II). Option (i) is correct.

 Question 15. How do you account for the strong reducing power for the Lithium in the aqueous solution?

Answer 15. Lithium has the highest negative EӨ value, that is –3.04V. Lithium has the small atomic size and the highest ionisation enthalpy, but it is compensated by the high hydration enthalpy. As a result, the reducing power of the Lithium is highest in the aqueous solution.

Question 16. Complete the following reactions given below:

(i) O2-2 + H2O →

(ii) O-2 + H2O →

Answer 16. (i) O2-2 + 2H2O → H2O2 + 2OH-

(ii) 2O2– + 2H2O → H2O2+ O2 + 2OH–

Question 17. Discuss the trend for the following:

(i) Thermal stability of the carbonates of the Group 2 elements.

(ii) The solubility and the nature of the oxides of the Group 2 elements.

Answer 17. (i) The thermal stability of the carbonates increases for the increase in the cationic size. The more stable the oxide of the alkaline earth metal, the less stable the carbonate for the same. So, BeCO3 is highly unstable, and the BeO is stable.

(ii) Alkali metals from the oxides with the oxygen and give the metal oxides. The oxides will be a basic exception to BeO as the BeO is amphoteric. They also react with the water to form the sparingly soluble hydroxides when the size of the cations increases, BeO and MgO have the highest lattice energy as well as they are insoluble in the water.

Question 18. Why are the BeSO4 and MgSO4 readily soluble in the water, whereas the CaSO4, SrSO4 and BaSO4 are insoluble?

Answer 18. BeSO4 and MgSO4 are readily soluble in the water, but CaSO4, SrSO4, and BaSO4 are insoluble. This is due to the greater hydration enthalpies of the Be2+ and Mg2+ ions. They overcome the lattice enthalpy factor, and thus, their sulphate is soluble in the water.

Question 19. All compounds of the alkali metals are easily soluble in the water, whereas the lithium compounds are more soluble in the organic solvents. Explain.

Answer 19. The alkali metal compounds form the ionic compounds because of their large ionic size and low ionization enthalpy, whereas Lithium forms the compounds of the covalent nature as their small ionic size, the high ionization enthalpy, and the high electronegativity.

Question 20. For the Solvay process, can we get the sodium carbonate directly treated with the solution containing the (NH4) 2CO3 with the sodium chloride? Explain.

Answer 20. For the Solvay process, the carbon dioxide is passed through the concentrated solution of the sodium chloride saturated with the ammonia, which forms ammonium carbonate, followed by the ammonium hydrogen carbonate. Ammonium hydrogen carbonate crystals separate as they are heated to form the sodium carbonate. The NH3 is recovered from the solution that contains the NH4Cl and then is heated when treated with Ca(OH)2. The reaction of the (NH4)2CO3 with the NaCl gives two products, Na2CO3 and NH4Cl, that are both soluble in the water that does not shift the equilibrium to the right.

Question 21. Write Lewis structure of the O-2 ion. Also, find out the oxidation state for each oxygen atom? What is the average oxidation state of the oxygen for this ion?

Answer 21. 

Source: Internet

Oxygen atoms with zero charges have six electrons. Thus the oxidation state is 0. If the oxygen atom has a negative charge, it has the seven electrons. Thus, the oxidation state is -1. The average oxidation state is 0 + (-1)/2 = -1/2.

 Question 22. What is the structure for the BeCl2 molecule in the gaseous and the solid state?

Answer 22. The gaseous/vapour state is different from the solid state. The structure of the BeCl2 in the solid-state is the polymeric chain structure. BeCl2 tends to form the chloro-bridged dimer at the temperatures below 1200K and dissociates into the linear monomer at the high temperatures of the order of 1200 K.

 Question 23. Beryllium and magnesium do not give colour for the flame, but the other alkaline earth metals do so. Why?

Answer 23. The valence electrons get excited to the higher energy level if the alkaline earth metal is heated.

It radiates energy that belongs to the visible region. If this excited electron comes back to the energy level that is low, the colour is seen. The electrons are firmly bound to the beryllium and magnesium. The energy needed to excite the electrons is very high. If the electron reverts back to the original position, the energy released does not fall in the visible region. So, no colour is observed in the flame.

Question 24. Potassium carbonate could be prepared by the Solvay process. Explain why?

Answer 24. The Solvay process is not applicable for the preparation of the potassium carbonate as the potassium carbonate is soluble in the water, and it doesn’t precipitate out as the sodium bicarbonate.

Question 25. Draw the structure for the (i) BeCl2 (vapour) (ii) BeCl2 (solid).

Answer 25. (i) BeCl2 has the linear structure and exists as the monomer in the vapour state.

(ii) For the solid phase, BeCl2 is the polymer.

Question 26. Describe the importance for the following : (i) limestone, (ii) cement, and (iii) plaster of Paris.

Answer 26. Uses of the cement:

• Construction of the bridge
• Plastering
• An essential ingredient in the concrete

Uses of the Plaster of Paris:

• Used to make the casts and the moulds
• Used to make the surgical bandages

Uses of the limestone:

• Preparation of the cement and the lime
• As a flux in the iron ore smelting

Question 27. Why are the lithium salts commonly hydrated, whereas the other alkali ions are usually anhydrous?

Answer 27. As Lithium has the smallest size for all the alkali metals, it can be easily polarised to water molecules. Therefore, the smaller the size of the ion, the greater is the ability to polarise the water molecules.

Therefore, the trihydrated Lithium Chloride and the other Lithium salts could be easily polarised. Because of this, the other alkali metal ions could only form the anhydrous salts.

 Question 28. What happens if:

(i) Sodium metal is immersed in the water?

(ii) Sodium metal is heated in the free supply of the air?

(iii) Sodium peroxide gets dissolved in the water?

Answer 28. (i) Sodium reacts to form the NaOH and H2 gas if it is dropped in the water. The reaction occurs as given below:

2Na(s) + 2H2O(l) 

2NaOH(aq) + H2(g)

(ii) Sodium peroxide is formed if sodium reacts with oxygen during heating it in the presence of air. The reaction proceeds as given below:

2Na(s)  + O2(s)  

Na2O2(s)

(iii) NaOH and water are formed as the result of the hydrolysis of the Sodium peroxide if it is dissolved in the water.

Na2O2(s) + 2H2O(l) 

2NaOH(aq) + H2O2(aq)

Question 29. How will you explain the following observations?

(i) BeO is almost insoluble, whereas the BeSO4 is soluble in the water.

(ii) BaO is soluble, whereas BaSO4 is insoluble in the water.

(iii) LiI is more soluble than KI in the ethanol.

Answer 29.

(i) The sizes of the Be2+ and O2- are small and are highly compatible with each other. As a result, the high amount of the lattice energy is released during the formation. The hydration energy if it is made to dissolve in the water is not enough for overcoming the lattice energy. So, BeO is almost insoluble in the water.

The size of the SO42- is large compared to the Be2+, and there is lesser compatibility and lattice energy that can be easily overcome by the hydration energy. Therefore, BeSO4 is easily soluble in the water.

(ii) The sizes of the Ba2+ and SO42- are large and are highly compatible with each other. As a result, the high amount of the lattice energy is released during their formation. The hydration energy if it is made to dissolve in the water is not enough for overcoming the lattice energy. So, BaSO4 is insoluble in the water.

The size of the O2- is small compared to the Ba2+, and there is lesser compatibility and lattice energy that can be easily overcome by the hydration energy. So, BaO is easily soluble in the water.

(iii) The lithium-ion has a smaller size, and as a result, it has the higher polarising capability. This enables it to polarise the electron cloud around the iodide ion, therefore, resulting in the greater covalent character in the LiI than KI. So, LiI is easily soluble in the ethanol.

Question 30. What are the common physical and chemical characteristics of the alkali metals?

Answer 30. Physical properties of the alkali metals:

(1) The alkali metal is soft. Hence, we can cut them easily. We can cut the sodium metal even when using the knife.

(2) Generally, the alkali metal is lightly coloured as well, as mostly they are seen as silvery white.

(3) Its atomic size is larger. Therefore, their density is low. The density of the alkali metal increases as we move down in the group from the Li to Cs, except for the K, which has lower density than the sodium.

(4)  Alkali metal has weak metallic bonding. Thus, they have low boiling and melting points.

(5) The salts present in the alkali metals expose colour to the flames as the heat of the flame excites the electrons, which are located on the outer orbital, to the higher energy level. For the excited state, electrons get reversed back to the ground level, and thus the emission of excess energy in the form of the radiation falls in the visible region.

(6) The metals like K and Cs lose electrons if they get irradiated with the light and also display the photoelectric effect.

Chemical properties of the alkali metals:

(1) Alkali metal reacts with the water and forms the oxides and hydroxides. Thus, the reaction will be more spontaneous when moving down the group.

(2) Alkali metal reacts with water as well as forms the dihydrogen and hydroxides.

General reaction:

2M + 2H20 

2M+ + 2OH– + H2   

(3) Dihydrogen reacts with the alkali metals and forms the metal hydrides. The hydrides formed have the higher melting points, and they are solids that are ionic.

2M + H2  

2M+ H–      

(4) Alkali metals directly react with the halogens and form the ionic halides except Li.

2M + CL2 

2MCI           (M = Li ,K, Rb, Cs)

It has the ability to easily distort the cloud, having the electrons that are around the –ve halide ion as the lithium-ion is smaller in size. So, the Lithium halide is naturally covalent.

(5) The alkali metals have strong reducing agents. This increases as we go down the group exception lithium. Due to the high hydration energy, it results in the strong reducing agent for all the alkali metals.

(6) For the blue-coloured solution(deep blue) that is naturally conducting, it gets dissolved in the liquid ammonia.

M +(x + y) NH3   

[ M ( NH3 )x ]+  +  [ e ( NH3)y ]–

 Question 31. Discuss the general features and trends in the properties of the alkaline earth metals

Answer 31. General features:

(i)  (Noble gas) ns2  is the electronic configuration of the alkaline earth metal.

(ii) To attain the nearest inert gas configuration, these metals lose two of the electrons. So its oxidation state is +2.

(iii)  The ionic radii and atomic radii are smaller in comparison with the alkali metals. When they moved down in the group, there was an increase in the trend of the ionic radii and atomic radii due as a result of the decrease in the effective nuclear charge.

(iv) The ionisation enthalpy is low as the alkaline earth metals are larger in size. The first ionisation enthalpy is higher in comparison with the metals of group 1.

(v) They appear as lustrous and silvery-white. They are soft like the alkali metals.

(vi) Factors that lead for the alkaline earth metals to have a high boiling point and melting points:

(*)  Atoms of alkali metals are larger than in comparison with the alkaline earth metals.

(*)  The strong metallic bonds are formed with the two valence electrons.

(vii) Ca- brick red; Sr- crimson red; Ba-apple green gives colours of the flames.

The electrons are bound strongly in the elements Be and Mg. Therefore, they do not give any colours for the flame.

The alkali metals are more reactive than the alkaline earth metals.

Chemical properties:

(i)  Reaction with the air and water:  Due to the formation of the oxide layer on the surface, beryllium and magnesium are most inert to the water and air.

(a)  BeO and Be3 N2 are formed if powdered Be is burnt in the air.

(b) In the formation of MgO and Mg3 N2, Mg is burnt when exposed to the air with dazzling sparkle as Mg is more electropositive.

(c) The formation of their respective nitrides and oxides is by the instant reaction of Sr, Ca, and Ba with air.

(d) Ca, Sr, and  Ba could react vigorously even with the water, which is cold.

(ii)  When they react with the halogens, halides are formed at high temperature.

M +X2   

MX2 (X = F,CL,Br,I)  

(iii)  Exception Be, all the alkaline earth metals react with the hydrogen to form hydrides.

(iv)  The alkaline earth metals instantly react with the acids to form salts along with the liberation of hydrogen gas.

M +2HCl

MCl2  + H2(X) 

(e) Reducing Nature: The alkaline earth metals are the strong reducing agents as the alkali metals, but the reducing power is less if compared to the alkali metals. In general, the reducing character increases from the top to the bottom.

(f) Solutions in the liquid ammonia: The alkaline earth metals dissolve in the liquid ammonia to give deep blue-black solutions like the alkali metals.

Benefits of Solving Important Questions of S-block Elements Class 11

Chemistry involves a theory as well as practical knowledge. Hence, it is essential for the students to have suitable study material with them. For this reason, we provide the important questions of Class 11 Chemistry Chapter 10 for students to have a strong command of the subject and gain mastery of it. You can get it from the Extramarks’ website anytime by registering on it.

Below are a few benefits of availing CBSE curriculum-based questions for Class 11 Chemistry:

•  It is written, explained, checked and verified by our experienced and knowledgeable teachers and mentors.
• It is trusted and relied upon by the lakhs of teachers and students around the country, ensuring students have suitable study material with them.
• The questions are covered from the NCERT textbooks, NCERT Exemplar and other reference books and sources for students to have a set of questions with them to practice.
• The solutions are given after analysing the CBSE’s latest curriculum, and thus, students solve with the right and proper steps in their examinations.
• All the formulas are listed so that students can quickly recall and revise before starting to practice the problems.

Extramarks provides quality resources like NCERT textbooks, NCERT revision notes, CBSE sample papers, CBSE past year question papers, and CBSE additional questions and mock tests for the students of Classes 1 to 12. Students must click on the links given below to access some of these resources:

• NCERT books
• CBSE Revision Notes
• CBSE syllabus
• CBSE sample papers
• CBSE past year’s question papers
• Important formulas 
• CBSE extra questions