Ncert Solutions Chemistry Class 11th
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11 months agoContributor-Level 10
Due to small size, the ionization enthalpies of Be and Mg are much higher than those of other alkaline earth metals. Therefore, a large amount of energy is needed to excite their valence electron, and that's why they do not impart colour to the flame.
New answer posted
11 months agoContributor-Level 10
Different concentrations of alkali metals in liquid ammonia gives different colours. The dilute solutions impart blue colour due to presence of ammoniated electrons whereas the concentrated solutions have copper bronze colour as ammoniated metal ions are bound by free electrons.
New answer posted
11 months agoContributor-Level 10
Potassium and caesium have much lower ionization enthalpy than that of lithium. As a result, these metals easily emit electrons on exposure to light. Due to this, K and Cs are used in photoelectric cells rather than lithium.
New answer posted
11 months agoContributor-Level 10
Alkali and alkaline earth metals are reducing agents. That is why these metals are not obtained by chemical reduction methods.
New answer posted
11 months agoContributor-Level 10
Both lithium and magnesium are harder and lighter than other elements in the respective groups.
Lithium and magnesium react slowly with water. Their oxides and hydroxides are much less soluble and their hydroxides decompose on heating. Both form a nitride, Li3N and Mg3N2, by direct combination with nitrogen.
The oxides, Li2O and MgO do not combine with excess oxygen to give any superoxide. (iv) The carbonates of lithium and magnesium decompose easily on heating to form the oxides and CO2. Solid hydrogen carbonates are not formed by lithium and magnesium.
Both LiCl and MgCl2are soluble in ethanol.
Both LiCl and MgCl2are deliquescent and cry
New answer posted
11 months agoContributor-Level 10
(i) Ionization enthalpy. Because of high nuclear charge the ionization enthalpy of alkaline earth metals are higher than those of the corresponding alkali metals.
(ii) Basicity of oxides. Basicity of oxides of alkali metals are higher than that of alkaline earth metals.
(iii) Solubility of hydroxides of alkali metals is higher than that of alkaline earth metals. Alkali metals due to lower ionization enthalpy are more electropositive than the corresponding group 2 elements.
New answer posted
11 months agoContributor-Level 10
It is because ionization enthalpy? Hi of potassium = 419 kJ mol-1. Ionization enthalpy of sodium = 496 KJ mol-1. Since Ionization enthalpy of potassium is less than that of sodium, potassium is more reactive than sodium.
New answer posted
11 months agoContributor-Level 10
Let x be the oxidation state of Na in Na2O2
Then, 2x + 2 (-1) = 0
=>2x – 2 = 0
=> x = +1.
New answer posted
11 months agoContributor-Level 10
All the alkali metals have one valence electron, ns1 outside the noble gas core. The loosely held s-electron in the outermost valence shell of these elements makes them the mostelectropositive metals, i.e. they readily lose electron to give monovalent M+ ions. Hence, they are never found in free state in nature.
New answer posted
11 months agoContributor-Level 10
The general characteristics and gradation in properties of alkaline earth metals are:
- Atomic size goes on increasing down the group.
- Ionisation energy goes on decreasing down the group.
- They are harder than alkali metals.
- They are less electropositive than alkali metals.
Electropositive character increases on going down the group.
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