Class 11th

Statement I is true because methyl orange indicator has pH range (3.2 to 4.2) which is suitable for buffer produced by strong acid and weak base.

Statement II is false because phenolphthalein has pH range (8.4 to 10.2) and only suitable for equivalence point above than 7, In this case pH increased by the addition of NaOH on acetic acid.

De-ionised water means dissolved minerals free water which is prepared by synthetic resin method. Where cation exchanged by H⁺ and anion exchanged by OH^- of resin.

$Ca{\left(OH\right)}_2+C{O}_2\to CaC{O}_3+H_{2}O$ (1st step of reaction)

$CaC{O}_3+H_{2}O+C{O}_2\to Ca{\left(HC{O}_3\right)}_2$ (2nd step of reaction)

Electronic configuration of $O_2^{-}$ anion is;

${\left(\sigma 1s\right)}^2{\left({\sigma }_{1s}^{*}\right)}^2{\left({\sigma }_{2s}\right)}^2{\left({\sigma }_{2s}^{*}\right)}^2{\left(\sigma 2pz\right)}^2{\left(\pi 2px\right)}^2={\left(\pi 2py\right)}^2{\left(\pi *2px\right)}^2={\left(\pi *2py\right)}^1$

In anion total 10 e^- resides in Bonding Molecular Orbitals and 7e^- resides in anti-Bonding Molecular orbitals. Hence bond order $=\frac{10-7}{2}=\frac{3}{2}=1.5.$

It is paramagnetic due to one unpaired electron.

Mass and temperature are scalars. We can fully describe them by magnitude alone and do not involve direction. 

Speed is a scalar quantity. It only has magnitude and no direction, unlike velocity, which is a vector.

Displacement, velocity, and acceleration are common vectors. These three vectors they have both magnitude and direction, and  follow vector addition rules.

Graphically, we place vectors head-to-tail. Analytically, we add components along axes using coordinate geometry, trigonometric functions, and unit vectors for precise vector resultant calculation.

It resolves vectors into components, adds corresponding x and y values algebraically, then reconstructs the resultant using magnitude and direction. That is, applying vector addition rules.