Chemistry

Kindly go through the solution 

When any change in matter is not responsible for changing the characteristic of the reaction,   the amount of matter we would have intensive properties. These properties, which we know as temperature or density,   remain constant even when the matter's size or quantity changes. On the other hand, we would have extensive properties in substances when they change when the amount or quantity in the system changes. 

Internal energy is the sum of all the energy in the system, as simple as that. But if we look into enthalpy, it is a state function that tells us how much internal energy is there in the system and how much work would be required to do to expand a gas against a constant pressure. 

For both work and heat, there are positive and negative signs, which mainly depend on transfer of energy. When work is done on the system, it will have a negative sign, but when work is done by the system, we will use a positive sign. This would be similar to how we view heat in chemical thermodynamics. If a system absorbs heat, it will be a positive sign. But if heat releases from a system, it will be a negative sign. 

${\left(\frac{C^{14}}{C^{12}}\right)}_t=\frac{{\left(\frac{C^{14}}{C^{12}}\right)}_{t=0}}{{\left(2\right)}^n}$

n = 3

t = 3 * 1580

= 4740 years

Amphoteric oxides are those which can react with both acid and base

SnO₂, PbO₂ and Al₂O₃ are amphoteric oxide

SiO₂, P₂O₅, CO₂ are acidic oxides

CO, NO and N₂O are neutral oxides

–C º N $?\underset{\begin{array}{l}\left|\text{?}\right|\\ O\end{array}}{C}$ , – CH₃ are –R group which is deactivating

– $\ddot{N}H$ – $\stackrel{\begin{array}{l}O\\ \left|\text{?}\right|\end{array}}{C}$ – CH₃ and – $\ddot{N}H$ – CH₃ due to presence of lone pair in nitrogen atom behaves as activating (+R) group.