Endothermic reactions - class-X

Option $E$ is the correct answer. Both the statements are incorrect.

Option B is the correct answer.

In exothermic reactions heat is liberated.

A reaction in which heat is released is called an exothermic reaction.

Oxygen and nitrogen do not react at ambient temperatures. But at high temperatures, they undergo an endothermic reaction producing various oxides of nitrogen. Such temperatures arise inside an internal combustion engine or a power station boiler, during the combustion of a mixture of air and fuel, and naturally in a lightning flash.

• All chemical reactions, including exothermic reactions, need activation energy to get started. Activation energy is needed so reactants can move together, overcome forces of repulsion, and start breaking bonds.
  
• If the molecules in the reactants collide with enough kinetic energy and this energy is higher than the transition state energy, then the reaction occurs and products form. In other words, the higher the activation energy, the harder it is for a reaction to occur and vice versa.
  
• Hence by the above points we can conclude that $\Delta H>E _a$ for exothermic reaction.

Reaction with the absorption of energy is called an endothermic reaction.
In the reaction 

Solution:- (B) Reaction $1$- endothermic, Reaction $2$- exothermic

Exothermic reactions are reactions or processes that release energy, usually in the form of heat or light. In an exothermic reaction, energy is released because the total energy of the products is less than the total energy of the reactants.
Endothermic reactions are reactions that require external energy, usually in the form of heat, for the reaction to proceed. Since endothermic reactions draw in heat from their surroundings, they tend to cause their environments to cool down. They are also generally non-spontaneous since endothermic reactions yield products that are higher in energy than the reactants. As such, the change in enthalpy for an endothermic reaction is always positive. 

In combustion of fuels such as woods.

Exothermic reactions are reactions or processes that release energy, usually in the form of heat or light. In an exothermic reaction, energy is released because the total energy of the products is less than the total energy of the reactants.
When quick lime reacts with water to form slaked lime , it releases a lot of energy . 
Endothermic reactions are reactions that require external energy, usually in the form of heat, for the reaction to proceed. Since endothermic reactions draw in heat from their surroundings, they tend to cause their environments to cool down. They are also generally non-spontaneous, since endothermic reactions yield products that are higher in energy than the reactants. 
When hydrogen reacts with iodine to form hydrogen iodide , it absorbs a lot of energy .

Evaporation is a process that requires energy (latent heat of vaporization) to turn a liquid into a gas. Because the petrol absorbs heat from the palm to evaporate, the palm feels cool, which is an endothermic process.

All the elements can easily gain an electron to form ions like $H^-$, $F^-$, $Cl^-$, and $O^{2-}$ atoms.

Energy is liberated (exothermic) when an electron is added to an atom or ion (electron affinity). Option C represents the combination of a positive ion and an electron to form a neutral atom, which releases energy.

The following are examples of endothermic reactions. They have a positive value of electron gain enthalpy and energy is absorbed when an electron is added to the atom.

Addition of quick lime to water and dilution of acid are examples of exothermic reactions.
The addition of quick lime (CaO) to water gives a hissing sound and is known as slaking of lime. It is an exothermic reaction with release of 15000 cal/mol
$CaO + H _2O \rightarrow Ca(OH) _2 + 15000  : cal$
Conc sulfuric acid has very high affinity for water. When sulfuric acid is mixed with water, a large amount of hat is released. The temperature may rise to as high as $120^o  : C$.
Hence, sulfuric acid is always diluted by adding acid to water.
On the other hand, evaporation of water and sublimation of Camphor are endothermic processes.

$C _6H _{12}O _6+6O _2\rightarrow 6CO _2+6H _2O$  is not endothermic reaction.
It is a synthesis reaction . the reaction is called cellular respiration as it produces energy for the body to use for activity. n oxidizing the glucose, the cell takes the energy from this chemical process and uses it for ATP synthesis. The ATP synthase is considered to be the most important carrier of energy in a cell. It captures energy, then uses that energy to fuel other processes within the cell. While most are formed during respiration, some are also made during photosynthesis.
Heat is not absorbed so it is not an endothermic reaction

When sodium reacts with water sodium hydroxide is formed and hydrogen gas is evolved.$2Na+2H _2O\rightarrow2NaOH+H _2$

The process of respiration is an oxidation reaction which is exothermic.
Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of heat energy. 

$C(g)+O _2(g)\rightarrow CO _2(g)+heat$

Quicklime is reacted with water to form calcium hydroxide.

Combustion or burning is a high temperature exothermic redox chemical reaction between fuel and an oxidant oxygen. Evaporation and sublimation are phase change physical process of water. Digestion of food is breakdown of larger molecules into small ones by bong breaking which is an endothermic process.

Combustion or burning is a high temperature exothermic redox chemical reaction between fuel and an oxidant oxygen. Bond breaking requires energy to be supplied for bond dissociation so it is an endothermic process while bond formation releases energy so that the product becomes stable which is an exothermic process.

A large amount of heat is released because the hydration reaction of sulfuric acid is highly exothermic and dilution should always be performed by adding the acid to the water rather than the water to acid. As hydration of sulfuric acid is thermodynamically favorable and the affinity of it for water is sufficiently strong.

If you pour a few drops of petrol on your palm.it will feel cool as the petrol evaporates this is a endothermic reaction.Because petrol is very volatile in nature, so when it evaporates.it absorb heat energy from the surroundings.

Exothermic Reaction: This is a chemical reaction that releases energy through light or heat.

During the dissolution of urea, heat is absorbed the term,dissolution,refers to a solute dissolving in a solvent to form a solution.In this experiment the solute is  solid urea.Urea being a molecular substance,does not dissociate into ions.The dissolution process involves adding energy to break the attractive forces between the molecules in the solid structure and releasing energy as the molecules form new attractive forces with the water molecules sourrounding it.

(A)In electrolysis of water heat energy is used to convert water into hydrogen and oxygen.

The internal energy of a larger chemical is smaller than that of the constituent ones. Hence energy is liberated when smaller components combine to form a large molecule. Hence the process is exothermic.

The term endothermic process describes the process or reaction in which the system absorbs energy from its surroundings; usually, in the form of heat. The opposite of an endothermic process is an exothermic process, one that releases, "gives out" energy in the form of heat.

An exothermic reaction is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation: reactants → products + energy.

(A) $HCl _{(l)}+H _2O _{(l)}\rightarrow HCl _{(aq)}+$ Heat (exothermic)

The decomposition of vegetable into compost is an example of  exothermic reaction.

$Si + C \rightarrow SiC$.

Since any chemical reaction requires some energy of activation to start with, so this step is endergonic or since biochemical reaction is also a type of chemical reaction, so its first step is endothermic or endergonic.

The neutralization reaction between a strong acid (HCl) and a strong base (KOH) is exothermic. The temperature rise depends on the heat released per mole of water formed; since the concentration and molar ratios remain the same in both experiments, the temperature rise T1 and T2 should be identical.

Combustion reaction are exothermic, hydrogenation of alkenes are exothermic and graphite is thermodynamically more stable.

The temperature of the reaction mixture rises beacause, the following exothermic reaction takes place:

Decomposition of ferrous sulphate is an endothermic reaction as it involves absorption of heat to form ferric oxide ($Fe _{2}O _{3}$), sulphur dioxide ($SO _{2}$) and sulphur trioxide ($SO _{3}$). The equation for this reaction can be written as:
$ 2FeSO _{4}(s)  \overset{heat}{\rightarrow}  Fe _{2}O _{3}(s)  +  SO _{2}(g)  +  SO _{3}(g)$

Reaction of sodium with hydrochloric acid is highly exothermic one and therefore explosive in nature.
$2Na(s)  +  2HCl(aq)  \rightarrow   2NaCl(aq)  +  H _{2}(g)$  +  heat

Dilution of sulphuric acid with water is a highly exothermic process as it occurs with the evolution of heat. The equation for this reaction  can be wriiten as:
$H _{2}SO _{4}  +  2H _{2}O  \rightarrow   2H _{3}O^{+}  +  SO _{4}^{2-}  +  heat$

1. Boiling of water would be an endothermic process because the system (water) is absorbing heat to turn into vapour. Hence both option 1 $ 3 are endothermic.
    And the reverse process would therefore be exothermic.
   
   2. Addition of Conc. acids to water is an exothermic reaction.

The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings in the form of heat where in case of exothermic it releases energy to the surroundings. 

An endothermic occurs if the products have a higher energy level than the reactants and $\Delta H$ will be positive. In other words, reactants have lesser energy than products.

In an exothermic reaction, the reacting mixture absorbs heat from the surroundings. Therefore, the reactants will have higher energy than the product here.

So the answer is option B.