Chemistry

10.3. Assertion: The alkalimetals and their salts impart characteristiccolour to an oxidizing flame.

Reason: This heat from the flame excites the outermost orbitalelectron to a higher energy level. When the excitedelectron comes back to the ground state, thereis emission of radiation in the visible region ofthe spectrum.

10.1.Assertion: The elements of Group 2 are commonly known asthe alkaline earth metals.

Reason: Theiroxides and hydroxides are alkaline in nature and thesemetal oxides are found in the earth's crust.

6.18 Giving examples differentiate between 'roasting' and 'calcination'.

The osmotic pressure of a solution of $\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$ is $0.10\mathrm{a}\mathrm{t}\mathrm{m}$ and that of a glucose solution is $0.20\mathrm{a}\mathrm{t}\mathrm{m}$ . The osmotic pressure of a solution formed by mixing $1\mathrm{L}$ of the sodium chloride solution with $2\mathrm{L}$ of the glucose solution is $\mathrm{x}*{10}^{-3}\mathrm{a}\mathrm{t}\mathrm{m}.\mathrm{x}$ is (nearest integer)(Solutions)

A $100\mathrm{m}\mathrm{L}$ solution was made by adding $1.43\mathrm{g}$ of ${\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3\cdot {\mathrm{x}\mathrm{H}}_2\mathrm{O}$ . The normality of the solution is $0.1\mathrm{N}$ . The value of $x$ is (The atomic mass of $\mathrm{N}\mathrm{a}$ is $23\mathrm{g}/\mathrm{m}\mathrm{o}\mathrm{l}$ )

The number of chiral centres present in threonine is(Biomolecules)

Consider the following equations :

$2{\mathrm{F}\mathrm{e}}^{2+}+{\mathrm{H}}_2{\mathrm{O}}_2\to \mathrm{x}\mathrm{A}+\mathrm{y}\mathrm{B}$ (in basic medium)

(in acidic medium)

$2{\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}+6{\mathrm{H}}^{+}+5{\mathrm{H}}_2{\mathrm{O}}_2\to {\mathrm{x}}^{\mathrm{\text{'}}}\mathrm{C}+{\mathrm{y}}^{\mathrm{\text{'}}}\mathrm{D}+{\mathrm{z}}^{\mathrm{\text{'}}}\mathrm{E}$

(in acidic medium)

The sum of the stoichiometric coefficients $x,y,x^{\mathrm{\text{'}}},y^{\mathrm{\text{'}}}$ and $z^{\mathrm{\text{'}}}$ for products $A,B,C,D$ and $E$ , respectively, is

The number of molecules with energy greater than the threshold energy for a reaction increases five fold by a rise of temperature from ${27}^{\circ }\mathrm{C}$ to ${42}^{\circ }\mathrm{C}$ . Its energy of activation in $\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}$ is (Take in $5=1.6094;\mathrm{R}=8.314\mathrm{J}{\mathrm{m}\mathrm{o}\mathrm{l}}^{-1}{\mathrm{K}}^{-1}$ )(Kinetics)