Category: Chemistry Questions

C3H8 + O2 ——-> CO2 + H2O

Balancing the equation

Comparing the number of reactants atoms with the number of products atoms.

First of all, list the number of each atom for the product and reactant, both sides of the equation.

Here in this example, listing the number of reactants and products can be written as

On the reactants side                                                On the product side

Carbon: 3                                                                                    Carbon: 1

Hydrogen: 8                                                                             Hydrogen: 2

Oxygen: 2                                                                                   Oxygen: 3

Writing the resultant equation

Now, after this, the first step to balance the number of carbon atoms is by multiplying the CO2 on the product side by 3. Therefore, the new equation will be then written as

C3H8 +O2 ——–> 3CO2 + H2O

As the carbon atoms are now balanced on each side, we will move further to balance the number of Hydrogen atoms.

The Hydrogen atoms at the reactant side are eight, whereas on the product side are two only, so multiplying the hydrogen on the product side will balance the number of the hydrogen atom. It makes sense, right?

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Let us see multiplying four on the product side will make what sort of difference. Writing the resultant equation,

C3H8 + O2 —–> 3CO2 + 4H2O

Now we have eight hydrogen atoms on each side, as we are left with Oxygen atoms only to balance; let us see how we can attain that.

As there are 10 Oxygen atoms on the product side and only two on the reactants side. So, we need to balance that as well, and therefore, multiplying the O2 atoms with five will make 10 Oxygen atoms overall on the reactant side. Let us move further with the balancing of the equation.

Multiplying 5 with O2 on the reactant side and writing the resultant equation

C3H8 + 5O2 ——–> 3CO2 + 4H2O

So, according to us, this is our balanced equation! Let us compare the number of atoms on each side.

On the Reactant side                                                 On the Product side 

Carbon: 3                                                                                    Carbon: 3

Hydrogen: 8                                                                             Hydrogen: 8

Oxygen: 10                                                                               Oxygen: 10

As the number of atoms on the products and reactant sides is equal, we can say that the equation is balanced.

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Bottom Line!

C3H8 + 5O2 ——–> 3CO2 + 4H2O is the final balanced equation of the given equation.

Don’t forget to try the same method to balance your other equations.

 

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An enthalpy change refers to the measure of heat absorbed or evolved. Let us get acquainted with everything you need to know about the Enthalpy change.

To better understand the energy change happening during a reaction, you need to understand the two parts of the universe, namely the surroundings and the system.

Surrounding refers to everything in the universe that is generally not a part of a system. The system relates to a matter’s specific position in a particular space studied during an observation or experiment.

Suppose a system loses a specific amount of energy. In that case, the same amount of energy is generally gained by the surroundings, whereas if a system gains a particular amount of energy, the same energy is supplied to by the surroundings.

• A physical change or a chemical reaction is endothermic if the system from the surroundings absorbs the heat.

• A physical change or chemical reaction is exothermic if the heat is liberated by the system into the surroundings.

What is Enthalpy?

Enthalpy refers to the heat changes in chemical reactions that are often measured in the laboratory under several conditions where the reacting system is open to the atmosphere. It’s a case where the system is at constant pressure.

So, we can say that the Enthalpy represented by H is the heat content of the system at a constant pressure. The changes in Enthalpy of a chemical system are routinely measured as the reactants are converted into products.

The heat released or absorbed by a reaction at constant pressure is similar to the enthalpy changes. It is given by the symbol ΔH.

 

Enthalpy Change

The enthalpy change of a reaction refers to the measure of differences in the Enthalpy of products and reactants. A system’s Enthalpy is generally identified by the energies required to break the chemical bonds and form chemical bonds.

 

A Thermochemical Equation

A thermochemical equation includes the enthalpy change of a reaction.

 

How do I know if the enthalpy change should be negative or positive?

A negative enthalpy change represents an exothermic reaction in which the energy is liberated from the reaction. In contrast, a positive enthalpy change represents an endothermic reaction in which the energy is taken in from the surroundings.

While deciding whether the change should be endothermic or exothermic and calculating the enthalpy change, you need to work on how many bonds are broken and how many bonds are formed.

The bond-breaking procedure requires energy, whereas the formation of the bond releases energy.

This applies to more than just the covalent bonds where attraction forces between the molecules are formed, which also applies to the energy release and vice versa.

In order to work out with the enthalpy change, we just add up the energies lost and gained in the reaction.

For instance, when working on the enthalpy formation of NaCl, when chlorine and sodium ions come together to generate NaCl.

NaCl is the one component of the overall reactions often known as lattice energy that we add up with several other components to identify the overall Enthalpy of formation.

 

So, should lattice enthalpy be negative and positive?

Bringing together the two oppositely charged ions, generating an ionic bond will liberate energy. It is an exothermic change where the lattice enthalpy must be negative.

 

When does the Enthalpy change positive or negative?

The enthalpy change ΔH is negative or positive is determined by

• ΔH is negative for the exothermic reactions that evolve heat to the surroundings.
• ΔH is positive for the endothermic reaction that absorbs heat from the surroundings.

 

Bottom Line!

The enthalpy change is negative or positive that is determined by the type of reaction. The Enthalpy is negative for exothermic reactions but is positive for endothermic reactions.

 

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Both the terms boiling and evaporation include changing a liquid form into a gas, but there are several differences between them. Let us get acquainted with the differences between both terms.

 

What is evaporation?

Evaporation refers to a process where the liquid form gets transformed to the vapor form. Let us take a simple example of evaporation and understand the process.

The evaporation process takes place when water gets evaporated from the soil by the sun’s heating effect. Evaporation takes place at any temperature and doesn’t produce bubbles.

In this process, the molecules or atoms in the liquid state gain adequate energy to transform into the gaseous state.

Therefore, it proceeds more quickly at high temperatures and high flow rates between liquid and gaseous phases in liquids having lower surface tension. So evaporation is considered a physical change.

For example, when you leave a water glass on a table for long enough, you will see that the water level will go down devoid of any interference from the side.

 

Factors affecting evaporation

• Surface Area

Evaporation is basically a surface phenomenon, and if the surface area is augmented, the evaporation rate also increases.

For instance, we generally spread clothes to dry them faster. So the relation between evaporation rate and surface area can be written as

Rate of Evaporation ∝ Surface area

• Humidity

Humidity refers to the water vapor amount present in the air. Air cannot hold more than a definite water vapor amount at a given temperature. In case the water amount in the air is high, then the evaporation rate decreases.

The relation between evaporation rate and surface area can be written as

Rate of Evaporation ∝1/Humidity

• Temperature

Evaporation rate increases at higher temperatures. With the increase in temperature, more particles get enough kinetic energy to go into the vapor state.

For instance, wet clothes dry rapidly under sunlight. The relation between evaporation rate and temperature can be written as

Rate of Evaporation ∝ Temperature

• Wind Speed

With the augment in the wind speed, the water vapor particles move away with the wind while decreasing the water vapor amount in the surrounding area. Therefore, an increase in the wind speed augments the evaporation rate.

The relation between evaporation rate and surface area can be written as

Rate of Evaporation ∝ Wind Speed

 

What is Boiling?

Boiling refers to a process of heating up the liquid where the liquid’s temperature is higher than a substance’s boiling point.

Boiling produces bubbles, and most liquids have a boiling point that results in more agitated and rapid movement within particles of a substance.

Here intense heat is added to the liquid molecules that begin moving rapidly throughout the substance.

Boiling can be determined when a liquid transcends the boiling point while leading to bubble formation. This states that a matter’s liquid state has entered into gaseous molecules.

 

Factors affecting Boiling Point

• Impurities

A compound’s boiling point is utilized as a reference property of it in a pure form.

For instance, pure water boils at 100℃, whereas water with several other substances boils at a higher temperature. Therefore it can be said that impurities in a pure substance lift up the boiling point.  

• Atmospheric Pressure

A substance’s boiling point modifies according to the pressure of its surrounding. At higher pressure, more energy is necessary to rupture the bonds between particles resulting in the augment of a boiling point.

Therefore the higher pressure boosts the boiling point, whereas the lower pressure depresses the boiling point.

 

Understanding the difference between evaporation and boiling

Parameters	Evaporation	Boiling
Process	Evaporation refers to a normal process that takes place when the liquid form changes to a gaseous form while leading to an increase in pressure or temperature.	Boiling refers to an unnatural process in which liquid gets heated and vaporized because of the continuous heating of the liquid.
Occurrence surface	It usually takes place on the liquid’s surface is heated up.	It takes place on the liquid’s entire mass that gets heated up.
Bubbling	The bubbling effect is not visible here.	The bubbling effect is visible here during the boiling process.
Speed	The evaporation process is slower and more carried out.	The process is much quicker and takes place rapidly.
Temperature required	A liquid evaporates at any temperature above freezing.	Boiling occurs only when the liquid reaches a specific temperature.
Source of energy	Evaporation utilizes the energy that is already present in the liquid.	Boiling requires external energy sources like a burner.
Time	It takes a longer time to complete	It takes a shorter period
Energy	It needs little or no energy	A lot of energy adds to the process

 

Bottom Line!

The primary difference noticed between both the terms is in their occurrence place where evaporation occurs on the surface of a liquid. In contrast, Boiling occurs over liquids with a large mass.

The rest differences are explained above. We hope that it gave you a clear idea about the dissimilarities.

 

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Oxidation number, often known as oxidation state, helps in describing the electron transfer. It is generally used in determining the changes occurring in redox reactions.

Let us first get acquainted with the oxidation numbers’ formal definition and move towards the calculative part of the query.

 

What is the oxidation number?

The oxidation number is described as the number allocated to the elements in a chemical combination.

It refers to the count of electrons that atoms present in a molecule can share, gain or lose while forming the chemical bonds with the different elements’ other atoms.

Formally the oxidation number of an atom is defined as the charge that an atom appears to have on the forming ionic bonds with other heteroatoms.

 

How to find an atoms’ oxidation number?

In the molecules, more electronegative atoms gain electrons from a lesser electronegative atom. It also has negative oxidation states. However, the oxidation state’s numerical value is equal to the number of electrons gained or lost.

The oxidation number of an atom is assigned by:

• Summing up the other atoms, molecules, or ions’ constant oxidation state that is bonded to it.
• Equating the ions’ or molecules’ total oxidation state to the total charge of the ion or molecule.

 

Calculating the oxidation number of Mn in K2MnO4

The oxidation number of an ion is generally the same as its charge. And we know that.

The oxidation number of K+ is +1

The oxidation number of O2- is -2

Now the remaining is Mn, and we don’t know the oxidation number of Mn.

Suppose the oxidation number of Mn is x

Here K+ has two ions that make +2

4 O2- ions that make it -8(4*-2)

In K2MnO2, as it is known that the molecule’s charge is neutral

Therefore, the overall oxidation number must be 0.

This means +2 (K) + x (Mn) + (-8) (O) = 0

Where, K= +1

This means that +2 (+1) + x (Mn) = 0 + 8

1 (x) = 8-2

Therefore, the value of x is +6.

So, the oxidation number of Mn is +6 in K2MnO4.

 

Bottom Line!

After calculating the entire equation, the oxidation number of Mn is +6 in K2MnO4.

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The atomic number for Lithium on the periodic table is 3.

The atomic number basically represents the total number of protons in an atom.

Therefore, the total number of protons in Lithium is 3.

While defining the atomic mass of an element, it is generally the number of neutrons and protons of an element.

As indicated on the periodic table, the atomic mass of Lithium is 7.

Therefore, the number of proton in Lithium = 3

Atomic Mass of the Lithium = 7

The atomic mass of an element = Number of Proton + Number of Neutron

Number of Neutron = Atomic mass of an element – Number of protons of the element

Number of Neutron = 7 – 3

This implies, Number of Neutron = 4

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Now, coming to the number of electrons of Lithium, as an atom is neutral in charge, the number of protons that are positively charged is equal to the number of electrons that are negatively charged.

Therefore, the electrons in a Lithium ion need to be 3 but lithium as a metal donates the electron.

So to have a+1 charge, Lithium must have lost an ion.

Therefore the number of electrons in Lithium is 2.

 

Bottom Line!

We can conclude that the Lithium ion has

Atomic number = 3

Atomic Mass = 7

Number of Protons = 3

Number of Neutrons = 4

Number of Electrons = 2

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“K” refers to the equilibrium constant of a chemical reaction. It provides insight into the relationship between the reactants and products when a chemical reaction reaches equilibrium.

 

For instance,

 

The concentration’s equilibrium constant denoted by Kc of a chemical reaction can be defined as the ratio of product’s concentration to reactant’s concentration. Each one raised their respective stoichiometric coefficients.

 

However, it is essential to be noted that the equilibrium constants are of several types that endow with relationships between reactants and products of equilibrium reactions in terms of different units.

 

At equilibrium, Forward reaction’s rate = Backward reaction’s rate

 

i.e. r_f= r_b

 

Given a reaction,

 

aA + bB ⇌ cC + dD

 

For the above reaction, the equilibrium constant is defined as:

Where K_c, indicates the equilibrium constant that is measured in moles per litre.

 

The unit of equilibrium constant = [Mole L^-1] ^△n

 

Where △n= Sum of product’s stoichiometric coefficients – Sum of reactant’s stoichiometric coefficients.

 

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