Question:

What are the common physical and chemical features of alkali metals ?

Answer:

Step 1: Understand the question.

Step 2: Research alkali metals to gain an understanding of their physical and chemical properties.

Step 3: Identify the common physical and chemical features of alkali metals.

Question:

Compare the alkali metals and alkaline earth metals with respect to (i) ionisation enthalpy (ii) basicity of oxides and (iii) solubility of hydroxides.

Answer:

(i) Ionisation Enthalpy: Alkali metals have lower ionisation enthalpy compared to alkaline earth metals.

(ii) Basicity of Oxides: Alkaline earth metals have higher basicity of oxides compared to alkali metals.

(iii) Solubility of Hydroxides: Alkali metals have higher solubility of hydroxides compared to alkaline earth metals.

Question:

Why are potassium and caesium used, rather than lithium used in photoelectric cells?

Answer:

1. Potassium and caesium are used in photoelectric cells because they have a larger number of electrons in their outer shell. This makes them better at emitting electrons when exposed to light.

2. Lithium has fewer electrons in its outer shell, making it less effective at emitting electrons when exposed to light. Therefore, lithium is less suitable for use in photoelectric cells.

Question:

When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.

Answer:

1. Alkali metals are highly reactive metals that react with liquid ammonia to form alkali metal amides.

2. When an alkali metal dissolves in liquid ammonia, the reaction produces an alkali metal amide and ammonia gas.

3. The reaction between the alkali metal and ammonia produces a range of different coloured compounds due to the different oxidation states of the alkali metal.

4. The oxidation state of the alkali metal determines the colour of the compound produced, and thus the colour of the solution. For example, potassium amide is yellow, while rubidium amide is purple.

Question:

K2​CO3​ cannot be prepared by Solvay’s process because: A KHCO3​ is less soluble than NaHCO3​ B KHCO3​ is too soluble to be precipitated by KCl and NH4​HCO3​ C K2​CO3​ is too soluble to be precipitated by KCl D K2​CO3​ is less soluble than Na2​CO3

Answer:

A) K2CO3 cannot be prepared by Solvay’s process because KHCO3 is less soluble than NaHCO3.

B) KHCO3 is too soluble to be precipitated by KCl and NH4HCO3.

C) K2CO3 is too soluble to be precipitated by KCl.

D) K2CO3 is less soluble than Na2CO3.

Question:

Why is Li2​CO3​ decomposed at a lower temperature whereas Na2​CO3​ at higher temperature?

Answer:

Step 1: Understand the difference between Li2CO3 and Na2CO3.

Step 2: Li2CO3 is a weaker electrolyte than Na2CO3, so it requires less energy to break down the ionic bonds.

Step 3: Therefore, Li2CO3 can be decomposed at a lower temperature than Na2CO3, which requires more energy to break down the ionic bonds.

Question:

The hydroxides and carbonates of sodium and potassium are easily soluble in water while the corresponding salts of magnesium and calcium are sparingly soluble in water. Explain.

Answer:

1. Hydroxides and carbonates are compounds that contain the elements hydrogen, oxygen, sodium, and potassium.

2. These compounds are easily soluble in water because the positively charged sodium and potassium ions are attracted to the negatively charged oxygen and hydrogen atoms in the water molecules.

3. The corresponding salts of magnesium and calcium, however, are not as easily soluble in water because the positively charged magnesium and calcium ions are not as strongly attracted to the negatively charged oxygen and hydrogen atoms in the water molecules.

4. This is why the hydroxides and carbonates of sodium and potassium are easily soluble in water while the corresponding salts of magnesium and calcium are sparingly soluble in water.

Question:

Describe the importance of the following : (i) limestone (ii) cement (iii) plaster of paris.

Answer:

(i) Limestone: Limestone is an important sedimentary rock composed mostly of calcium carbonate. It is used in a variety of construction projects, such as road construction, building foundations, and mortar. It is also used to make cement and plaster of paris.

(ii) Cement: Cement is a binding material used in construction. It is made from a mixture of limestone, clay, and other materials such as iron oxide. Cement is used to bind together masonry, concrete, and other building materials.

(iii) Plaster of Paris: Plaster of Paris is a type of plaster made from gypsum. It is used for a variety of applications, including creating sculptures, casts for broken bones, and for covering walls and ceilings. It is also used to create molds for concrete and other building materials.

Question:

Which of the alkali metal is having least melting point ? A Na B K C Rb D Cs

Answer:

1. Alkali metals are group 1 elements in the periodic table.

2. The melting points of alkali metals generally decrease as you move down the group.

3. The least melting point among the alkali metals is Cesium (Cs), with a melting point of 28.4°C.

4. Therefore, the answer is D) Cs.

Question:

The thermal stability of alkaline earth metal carbonates- MgCO3​,CaCO3​,SrCO3​ and BaCO3​, follows the order: A BaCO3​>SrCO3​>CaCO3​>MgCO3​ B CaCO3​>SrCO3​>MgCO3​>BaCO3​ C MgCO3​>CaCO3​>SrCO3​>BaCO3​ D BaCO3​>SrCO3​>MgCO3​>CaCO3

Answer:

Answer: A BaCO3​>SrCO3​>CaCO3​>MgCO3​

Question:

Discuss the general characteristics and gradation in properties of alkaline earth metals.

Answer:

1. Begin by defining alkaline earth metals, which are a group of elements in the periodic table that includes beryllium, magnesium, calcium, strontium, barium, and radium.

2. Explain the general characteristics of alkaline earth metals, such as their silvery-white appearance, low reactivity, and high densities.

3. Discuss the physical and chemical properties of alkaline earth metals, such as their high melting and boiling points, low electronegativity, and high reactivity in water.

4. Explain the gradation in properties of alkaline earth metals, such as their increasing reactivity and decreasing melting and boiling points as the atomic number increases.

5. Conclude by summarizing the general characteristics and gradation in properties of alkaline earth metals.

Question:

Why are alkali metals not found in nature?

Answer:

1. Alkali metals are very reactive elements, meaning they react easily with other elements.

2. When alkali metals react with other elements, they form compounds that are not found naturally in the environment.

3. Therefore, alkali metals are not found in nature because they form compounds that are not naturally occurring.

Question:

Explain why is sodium less reactive than potassium.

Answer:

1. Sodium and potassium are both alkali metals and are both highly reactive.
2. Sodium has a single electron in its outermost shell, while potassium has two electrons in its outermost shell.
3. This means that potassium has a stronger hold on its outermost electrons, making it harder for it to give them away and form compounds.
4. Sodium, on the other hand, has a weaker hold on its outermost electron, making it easier for it to give it away and form compounds.
5. This makes potassium less reactive than sodium, since it is harder for it to form compounds.

Question:

In what ways lithium shows similarities to magnesium in its chemical behaviour?

Answer:

1. First, it is important to understand the chemical properties of lithium and magnesium.
2. Both lithium and magnesium are alkali metals, meaning they have a single valence electron in their outer shell and they are highly reactive.
3. Both elements form ionic compounds with other elements and have similar reactivity with water, oxygen, and halogens.
4. Both lithium and magnesium have a similar ability to form complex compounds with other elements.
5. Both elements have similar reactivity with acids and bases, and they can form similar compounds with other elements in their group.
6. Finally, both elements have similar solubility in water and other solvents.

Question:

Compare the solubility and thermal stability of the following compounds of the alkali metals with those of the alkaline earth metals. (a) Nitrates, (b) Carbonates, (c) Sulphates.

Answer:

a) Nitrates: The solubility of nitrates for alkali metals is generally greater than for alkaline earth metals. Alkali metals have higher thermal stability for nitrates than alkaline earth metals.

b) Carbonates: The solubility of carbonates for alkali metals is generally lower than for alkaline earth metals. Alkali metals have lower thermal stability for carbonates than alkaline earth metals.

c) Sulphates: The solubility of sulphates for alkali metals is generally lower than for alkaline earth metals. Alkali metals have lower thermal stability for sulphates than alkaline earth metals.

Question:

Describe two important uses of each of the following: (i) caustic soda (ii) sodium carbonate (iii) quicklime.

Answer:

(i) Caustic Soda:

1. Caustic soda is used in the production of paper, textiles, and soaps.
2. It is also used as a cleaning agent to unclog drains and remove grease and oil from surfaces.

(ii) Sodium Carbonate:

1. Sodium carbonate is used in the production of glass, detergents, and other products.
2. It is also used for water softening and as a food additive to improve texture and flavor.

(iii) Quicklime:

1. Quicklime is used as a soil conditioner and fertilizer.
2. It is also used in the production of cement and as a flux in steelmaking.

Question:

Draw the structure of (i) BeCl2​ (vapour) (ii) BeCl2​ (solid).

Answer:

(i) BeCl2 (vapour): The vapour form of BeCl2 is a diatomic molecule. It has a linear structure, with one Be atom at the center and two Cl atoms at the ends.

(ii) BeCl2 (solid): The solid form of BeCl2 is a covalent compound. It consists of two Be atoms and two Cl atoms arranged in a tetrahedral structure. Each Be atom is surrounded by four Cl atoms, and each Cl atom is surrounded by one Be atom.

Question:

Why are lithium salts commonly hydrated and those of the other alkali ions usually anhydrous?

Answer:

1. Lithium salts are commonly hydrated because they are more soluble in water than other alkali ions.

2. This is due to the smaller size of the lithium ion, which creates weaker electrostatic interactions with water molecules compared to other alkali ions.

3. As a result, the hydration of lithium salts is more favorable than the hydration of other alkali ions, making them more likely to be hydrated.

4. On the other hand, other alkali ions are usually anhydrous because they have larger sizes and stronger electrostatic interactions with water molecules, making it more difficult for them to dissolve in water.

Question:

Comment on each of the following observations: (a) The mobilities of the alkali metal ions in aqueous solution are Li+<Na+<K+<Rb+<Cs+. (b) Lithium is the only alkali metal to form a nitride directly. (c) E⊖ for M2+(aq)+2e−→M(s) (where M=Ca,Sr or Ba) is nearly constant.

Answer:

a) The observation is accurate; the mobilities of the alkali metal ions in aqueous solution increase in the order Li+<Na+<K+<Rb+<Cs+. This is due to the fact that the size of the ions increases down the group, and larger ions have higher mobilities in aqueous solution.

b) This observation is also true; lithium is the only alkali metal to form a nitride directly. This is because lithium is the lightest alkali metal, and its small size allows it to form strong bonds with nitrogen atoms.

c) The observation is accurate; the standard electrode potential (E⊖) for M2+(aq)+2e−→M(s) (where M=Ca,Sr or Ba) is nearly constant. This is because all of these metals have similar electronegativities and are therefore able to form strong bonds with other atoms. As a result, the energy required to form the metal is nearly the same for each of them.

Question:

Write balanced equations for reactions between: (a) Na2​O2​ and water (b) KO2​ and water (c) Na2​O and CO2​.

Answer:

(a) 2Na2​O2​ + 4H2​O → 4NaOH + O2​

(b) 2KO2​ + 2H2​O → 2KOH + O2​

(c) Na2​O + CO2​ → Na2​CO3

Question:

How would you explain the following observations?(i) BeO is almost insoluble but BeSO4​ is soluble in water.(ii) BaO is soluble but BaSO4​ is insoluble in water.(iii) LiI is more soluble than KI in ethanol.

Answer:

(i) BeO is almost insoluble because it is an ionic compound and the large size of the Be2+ ion makes it difficult for it to dissolve in water. BeSO4, however, is soluble because the sulfate ion is a much smaller ion and can more easily dissolve in water.

(ii) BaO is soluble because the Ba2+ ion is much smaller than the Be2+ ion, and therefore it is more easily able to dissolve in water. BaSO4, however, is insoluble because the sulfate ion is a much larger ion, and it is too large to dissolve in water.

(iii) LiI is more soluble than KI in ethanol because Li+ is a smaller ion than K+, and therefore it is more easily able to dissolve in ethanol.

Question:

Beryllium and magnesium do not give colour to flame whereas other alkaline earth metals do so. Why?

Answer:

Step 1: Alkaline earth metals are a group of elements in the periodic table.

Step 2: Beryllium and magnesium are two of the alkaline earth metals.

Step 3: The other alkaline earth metals, such as calcium, strontium, and barium, are known to give a colour to flame when they are heated.

Step 4: Beryllium and magnesium, however, do not give a colour to flame when heated.

Step 5: This is because beryllium and magnesium have a much lower ionization energy than the other alkaline earth metals, which means that they do not release enough energy when heated to cause the electrons in the flame to be excited and emit visible light.

Question:

What happens when:(i) magnesium is burnt in air (ii) quick lime is heated with silica (iii) chlorine reacts with slaked lime (iv) calcium nitrate is heated

Answer:

(i) When magnesium is burnt in air, it reacts with oxygen to form magnesium oxide.

(ii) When quick lime is heated with silica, it forms calcium silicate.

(iii) When chlorine reacts with slaked lime, it forms calcium chloride and water.

(iv) When calcium nitrate is heated, it decomposes into calcium oxide, nitrogen dioxide, and oxygen.

Question:

Why is LiF almost insoluble in water whereas LiCl soluble not only in water but also in acetone?

Answer:

1. LiF is an ionic compound made up of Li+ ions and F- ions.

2. LiF has strong electrostatic forces of attraction between the positively charged Li+ ions and the negatively charged F- ions, which makes it difficult for the ions to separate and dissolve in water.

3. LiCl is also an ionic compound made up of Li+ ions and Cl- ions.

4. LiCl has weaker electrostatic forces of attraction between the positively charged Li+ ions and the negatively charged Cl- ions, which makes it easier for the ions to separate and dissolve in both water and acetone.

Question:

What happens when:(i) sodium metal is dropped in water?(ii) sodium metal is heated in free supply of air?(iii) sodium peroxide dissolves in water?

Answer:

(i) When sodium metal is dropped in water, it will react with the water to produce hydrogen gas and sodium hydroxide.

(ii) When sodium metal is heated in a free supply of air, it will react with the oxygen in the air to form sodium oxide.

(iii) When sodium peroxide dissolves in water, it will break down into sodium ions and peroxide ions, which will react with the water to form hydrogen peroxide and sodium hydroxide.

Question:

Which one of the following alkali metals gives hydrated salts?A LiB NaC KD Cs

Answer:

A. K

Question:

Find out the oxidation state of sodium in Na2​O2​.

Answer:

Answer:

1. The oxidation state of sodium in Na2​O2​ is +1.

Question:

Explain why can alkali and alkaline earth metals not be obtained by chemical reduction methods?

Answer:

1. Alkali and alkaline earth metals are very reactive elements and are highly likely to react with other elements.

2. This means that they cannot be isolated by chemical reduction methods, as the reducing agents used in these methods would react with the alkali and alkaline earth metals, rather than reducing them.

3. Furthermore, these elements are found in nature in their elemental form, and so are not typically reduced from other compounds.

Question:

Discuss the various reactions that occur in the Solvay process.

Answer:

1. Define the Solvay process: The Solvay process is an industrial process used to manufacture sodium carbonate (Na2CO3) from sodium chloride (NaCl), ammonia (NH3), and carbon dioxide (CO2).

2. Explain the chemical reactions involved in the process: The Solvay process involves a series of chemical reactions that take place in four steps. In the first step, sodium chloride is dissolved in water to form a brine solution. In the second step, ammonia is added to the brine solution, which produces ammonium chloride (NH4Cl). In the third step, carbon dioxide is bubbled through the solution, which reacts with the ammonium chloride to form ammonium bicarbonate (NH4HCO3). Finally, in the fourth step, the ammonium bicarbonate is heated to form sodium carbonate (Na2CO3) and water.

3. Discuss the implications of the process: The Solvay process is an efficient and cost-effective way of producing sodium carbonate, which is an important industrial chemical. It also reduces the amount of waste produced, as the by-products of the process are non-toxic and can be reused. However, it does require large amounts of energy, and the production of ammonia is a major source of air pollution.

Question:

Starting with sodium chloride how would you proceed to prepare (i) sodium metal, (ii) sodium hydroxide, (iii) sodium peroxide, (iv) sodium carbonate?

Answer:

(i) Sodium Metal:

1. Heat sodium chloride in an electric arc furnace to produce molten sodium chloride.
2. Electrolyze the molten sodium chloride to separate the sodium metal from the chlorine gas.

(ii) Sodium Hydroxide:

1. Heat sodium chloride in a chemical reactor to produce sodium chloride and chlorine gas.
2. React the chlorine gas with water to produce hydrochloric acid.
3. React the hydrochloric acid with sodium hydroxide to produce sodium hydroxide.

(iii) Sodium Peroxide:

1. Heat sodium chloride in a chemical reactor to produce sodium chloride and chlorine gas.
2. React the chlorine gas with oxygen to produce sodium peroxide.

(iv) Sodium Carbonate:

1. Heat sodium chloride in a chemical reactor to produce sodium chloride and chlorine gas.
2. React the chlorine gas with sodium hydroxide to produce sodium hypochlorite.
3. React the sodium hypochlorite with carbon dioxide to produce sodium carbonate.

Question:

Explain the significance of sodium, potassium, magnesium and calcium in biological fluids.

Answer:

1. Sodium, potassium, magnesium and calcium are essential minerals that play important roles in biological fluids.

2. Sodium helps maintain the balance of fluids in the body, helps regulate blood pressure and nerve impulse transmission, and is necessary for muscle contraction.

3. Potassium helps maintain the balance of fluids in the body, helps regulate heart rate and blood pressure, and is necessary for muscle contraction.

4. Magnesium helps regulate nerve and muscle function, helps regulate blood pressure, and is necessary for the production of energy.

5. Calcium helps build and maintain strong bones and teeth, helps regulate nerve and muscle function, and helps regulate the release of hormones.

6. In summary, sodium, potassium, magnesium and calcium are essential minerals that are necessary for proper functioning of the body and are essential components of biological fluids.

Question:

State as to why: (a) a solution of Na2​CO3​ is alkaline ? (b) alkali metals are prepared by electrolysis of their fused chlorides ? (c) sodium is found to be more useful than potassium ?

Answer:

(a) A solution of Na2CO3 is alkaline because Na2CO3 is a base and bases have a pH greater than 7.

(b) Alkali metals are prepared by electrolysis of their fused chlorides because electrolysis is a process which uses electricity to separate a compound into its component ions. The fused chlorides of the alkali metals are solid at room temperature and can be easily ionised in an electrolytic cell.

(c) Sodium is found to be more useful than potassium because sodium has a lower ionization energy than potassium, meaning that it is easier to remove electrons from sodium atoms than from potassium atoms. This makes sodium more reactive and therefore more useful in a variety of applications.