Science Teacher

Chemistry
-->Atomic structure

An orbit where electron doesn't lose it energy as it moves within it is called ?

A. Planetary orbit
B. Stationary orbit
C Earth orbit

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Chemistry
-->Atomic structure

As long as an electron moves in an a particular orbit it doesn't lose it energy

A. Yes
B. No
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Chemistry FAQ

A frequently asked question;

Q: How do you even know a reaction is endothermic or exothermic ?

------'Answer '--------

You can deduce if a reaction is exothermic or endothermic from the heat change or enthalpy of the system.
By system, I mean reaction.
Now what is enthalpy or heat change ? Enthalpy is the heat content available in a reaction or system. It is also the amount of energy available in the system.
The symbol from heat change or enthalpy is delta H or a triangle shape written beside an H.
(Check previous post for that).
Now a reaction is EXOTHERMIC if the enthalpy is written in negative figure e.g (delta H = -189°C)
A reaction is ENDOTHERMIC if the enthalpy is written in positive figure e.g (delta H = 189°C)

You can also deduce if a reaction is exothermic or endothermic from the information given in questions.
A question could come in the form ;
The reaction between Nitrogen and Hydrogen to form ammonia gives off heat to the surrounding. What is the coefficient of the heat change or heat type reaction is it ?
The answer is simply exothermic and negative.
The coefficient of the heat change will be negative because it gives off heat to the surrounding a major characteristics of exothermic reaction. (check previous for the definition of exothermic reaction).

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Consider the reaction:

N₂ + 3H₂ ↔ 2NH₃

all in gaseous state catalysed by iron at 500ᵒC

GIVEN; ΔH = -91ᵒC
what is the effect of temperature on the system ?

---solution-----

from the enthalpy of the system we could deduce that it is an exothermic reaction.
by definition an exothermic reaction gives off heat to the surroundings while endothermic absorbs heat from the surroundings.
since this reaction is exothermic then, the FORWARD reaction gives off heat i.e formation of ammonia while reverse or backward reaction absorbs heat i.e the formation of hydrogen and nitrogen from ammonia back.

Therefore, an increase in temperature favors the BACKWARD reaction. this is because an increase in temperature of a system favours the side absorbing heat and vice versa.

from this reaction , the forward reaction is giving off heat while the backward reaction is absorbing heat so since increase in temp. favors the side which absorbs heat , then an increase in temperature favors backward reaction.

read well and digest
see you in the next post ......

Fact about a system in equilibrium

for a reaction to attain equilibrium;
-It must be in a closed system i.e no energy should be lost through the system or gained into the system
-for the above to be achieved the temperature, pressure and concentration of the system remains constant.
-it must be a reversible reaction (an irreversible reaction cannot attain equilibrium)
-the Gibbs free energy i.e the energy available to do work must be zero, ∆G = 0
-the rate of forward reaction must be equal to backward reaction

keep this for now and watch out for next post ......

Did you know !

That the main constituent of LPG is butane.
It also contains a fraction of ethane and propane.

LPG simply translate to Liquified Petroleum Gas.
It is a gaseous fuel.
Another gaseous fuel is the Natural gas its main constituent is Methane.

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Today's chemistry

In which of the following alternatives was it proved that H20 and H202 obey the law of multiple proportion

A. The hydrogen are combined In a simple ratio of 1:2
B. The hydrogen are combined in a simple ratio of 2:1
C. The oxygen atoms are combined in a simple ratio of 1:2
D. The oxygen atoms are combined in a simple ratio of 2:1
E. None of the above

Today's Biology

A substance that impregnate the walls of a tracheophyte cells to provide a necessary stiffness for structural support is

A. Tanin
B. Chitin
C. Lignin
D. Nectar
E. None of these

Questions on the previously taught today's Biology

DIR: try to answer

1. Which information is given in a species name
A. genus and order
B. Division and genus
C. genus and species identifier
D. Species identifier and phylum

2. To which level of classification does a group closely related species of organisms belong ?
A. Class
B. Order
C. Genus
D. Kingdom

3. Every organism is group under the

A. Kingdom monera , protista , fungi , plantae , animalia
B. Bacteria , Archea and Eukarya
C. Kingdom animalia
D. Domain eukarya

Today's Biology

The three (3) domains of life include;

1. Domain bacteria
2. Domain archae
3. Domain eukarya

All the other six kingdoms are grouped under this thre Domains

1. Under bacteria we have : Eubacteria (true bacteria)

2. Under Archae we have : Archaebacteria

3. Under eukarya falls the remaining four

i Kingdom protista
ii kingdom fungi
iii Kingdom plantae
iv Kingdom animalia

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The maximum number of electrons, present in an orbit whose angular momentum is 2h/pie ?

A. 2
B. 8
C. 18
D. 32

Solution

According to bohr atomic model
Angular momentum of electron equals = nh/ £

Here I'll use the sign £ to mean pie

That is,

mvr = nh/£

But in the question we were given 2h/£

Comparing nh/£ and 2h/£ , we have ;

nh/£ = 2h/£

From here n = 4£h /£h
Then n = 4

You've to understand that the number of electrons in an orbit or main energy level is given as : 2n²
Where n = principal quantum number
From the question n equals 4

Then the number of electrons in the main energy level or orbit is

2n²=2(4)² = 32

Therefore , the max. No of electrons will be 32 electrons
Option (D) ✅️🔰

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