Answer:
The answer is: (a) positive; (b) negative.
Explanation:
The change in enthalpy (ΔH) of a reaction is the amount of energy absorbed or released during a chemical reaction carried out at constant pressure.
a) In an endothermic chemical reaction, heat energy is absorbed by the system from the surrounding. Therefore, the sign of enthalpy change for an endothermic process is positive, ΔH= positive.
b) In an exothermic chemical reaction, heat energy is released by the system into the surrounding. Therefore, the sign of enthalpy change for an exothermic process is negative, ΔH= negative.
Sharing of electrons always means its a covalent bond, and unequal means it is polar, so it is a polar covalent bond
Answer:
The correct answer is - D C2H4.
Explanation:
Saturated hydrocarbons are hydrocarbons with single covalent C-C bonds. They are known as alkanes. The general formula for these hydrocarbons is CnH2n+2
Unsaturated hydrocarbons the hydrocarbons with double or triple covalent C-C bonds. They are known as alkenes and alkynes respectively. The general formula for these hydrocarbons is CnH2n and CnHn-2
For the given options:
Option D: C2H4, is the simplest alkene with a double bond so it is an unsaturated hydrocarbon.
