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.
(i) Nitrates
Thermal stability
Nitrates of alkali metals, except LiNO3, decompose on strong heating to form nitrites.
2KNO3 (s) → 2KNO2(s) +O2(g)
LiNO3, on decomposition, gives oxide.
2LiNO3(s) Li2O(s) + 2 NO2(g) + O2(g)
Similar to lithium nitrate, alkaline earth metal nitrates also decompose to give oxides.
2Ca(NO3)(s) 2CaO(s) + 4 NO2(g) + O2(g)
As we move down group 1 and group 2, the thermal stability of nitrate increases.
Solubility
Nitrates of both group 1 and group 2 metals are soluble in water.
(ii) Carbonates
Thermal stability
The carbonates of alkali metals are stable towards heat. However, carbonate of lithium, when heated, decomposes to form lithium oxide. The carbonates of alkaline earth metals also decompose on heating to form oxide and carbon dioxide.
Solubility
Carbonates of alkali metals are soluble in water with the exception of Li2CO3. Also, the solubility increases as we move down the group. Carbonates of alkaline earth metals are insoluble in water.
(iii) Sulphates
Thermal stability
Sulphates of both group 1 and group 2 metals are stable towards heat.
Solubility
Sulphates of alkali metals are soluble in water. However, sulphates of alkaline earth metals show varied trends.
BeSO4 Fairly soluble
MgSO4 Soluble
CaSO4 Sparingly soluble
SrSO4 Insoluble
BaSO4 Insoluble
In other words, while moving down the alkaline earth metals, the solubility of their sulphates decreases.
Compare the alkali metals and alkaline earth metals with respect to
(i) ionization enthalpy
(ii) basicity of oxides and
(iii) solubility of hydroxides.
Discuss the various reactions that occur in the Solvay process.
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) (where M = Ca, Sr or Ba) is nearly constant.
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
State as to why
(a) a solution of Na2CO3 is alkaline ?
(b) alkali metals are prepared by electrolysis of their fused chlorides ?
(c) sodium is found to be more useful than potassium ?
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3 at higher temperature?
In what ways lithium shows similarities to magnesium in its chemical behaviour?
Find the oxidation state of sodium in Na2O2.
Explain why is sodium less reactive than potassium?
How do you account for the formation of ethane during chlorination of methane?
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4
Assign oxidation number to the underlined elements in each of the following species:
(a) NaH2PO4
(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
What is the basic theme of organisation in the periodic table?
Explain the formation of a chemical bond.
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only.
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
Do you observe any soil pollution in your neighbourhood? What efforts will you make for controlling the soil pollution?
Write chemical reactions to show the amphoteric nature of water.
If the photon of the wavelength 150 pm strikes an atom and one of its inner bound electrons is ejected out with a velocity of 1.5 × 107 ms–1, calculate the energy with which it is bound to the nucleus.
If the density of methanol is 0.793 kg L–1, what is its volume needed for making 2.5 L of its 0.25 M solution?
What are allotropes? Sketch the structure of two allotropes of carbon namely diamond and graphite. What is the impact of structure on physical properties of two allotropes?
How much time would it take to distribute one Avogadro number of wheat grains, if 1010 grains are distributed each second?
What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.
(i) F–
(ii) Ar
(iii) Mg2+
(iv) Rb+
Calculate the wavelength for the emission transition if it starts from the orbit having radius 1.3225 nm and ends at 211.6 pm. Name the series to which this transition belongs and the region of the spectrum.
In Rutherford’s experiment, generally the thin foil of heavy atoms, like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like aluminium etc. is used, what difference would be observed from the above results?
What properties of water make it useful as a solvent? What types of compound can it (i) dissolve, and (ii) hydrolyse?
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