Topics in ChemistryLe Chatelier's Principle: Changes in concentration and pressure in dynamic equilibrium Chemical Equilibrium: Dynamic Equilibrium in Chemistry Static and Dynamic Equilibrium explained with their Differences Chemistry Scheme of Work, SS1, First Term Chemistry Scheme of Work, SS1, Second Term Chemistry Scheme of Work, SS1, Third Term Compounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures Mixtures: Characteristics of Mixtures Physical Properties of Matter explained with Examples Chemical Properties of Matter explained with Examples Differences between Physical and Chemical Change Ionic Theory and Electrolysis Physical and Chemical Properties of Acids States of Matter: Characteristics of Solids Liquid State of Matter: Characteristics of Liquids Gaseous State of Matter: Characteristics of Gases Molar Mass, Worked Examples and Differences with Molecular Mass Elements: Characteristics of Elements Salts and Types of Salt in Chemistry
Academic Questions in Chemistry
The simplest formula of a compound is termed _____.
A. Emperical formula
B. Molecular formula
C. Avogadro's number
D. Mass formula
E. Molar mass formula
F. Mole ratio
A compound composed of iron (Fe) and oxygen (O) was analyzed and found to contain 69.94% iron and 30.06% oxygen. Find the empirical formula of the compound. (Molar mass of Fe=55.85, O=16)
Which of the following statement is false concerning hydrocarbons?
A. Hydrocarbons can be aromatic
B. Hydrocarbons are made up of carbon and hydrogen only
C. Alkynes are aliphatic hydrocarbons
D. Alkenes have a carbon-carbon double bond in their structure
E. Benzene ring has a carbon-carbon triple bond in its structure
F. Hydrocarbons are the main constituents of petroleum and natural gas
The ability of carbon to form long chain of itself is called _____.
A. Carbon chain reaction
E. Organic chemistry
F. Carbon moleculation
Calculate the relative molecular mass of methane. (Carbon = 12.001, H = 1.00794).
A. 13.00894 amu
B. 11.00206 amu
C. 12.00794 amu
D. 14.001 amu
E. 15.001 amu
F. 16.033 amu
Which of he following is not a fact concerning gold?
A. 24 karat gold is the purest gold element
B. It is the 50th rarest metal amongst all elements found beneath the earth crust
C. It is the most malleable and ductile pure metal ever known
D. It is the only metal with a golden color
E. Gold is non toxic and can be eaten with food
F. It's present inside the earth crust in all seven continents
Which of the following is not an example of a chemical change?
Which of the following is not a fraction of crude oil?
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In chemistry, chemical equilibrium is often referred to as dynamic equilibrium.
Recall that the word 'equilibrium' in English refers to a state of balance or stability. However, dynamic equilibrium in chemistry focuses on the stability of reaction rate between reactants and products in a chemical reaction.
Note: Chemical or Dynamic equilibrium will only occur in a reversible reaction which is always denoted by the forward and backward arrow signs (⇌). An instance is shown in the formation of ammonia (NH3) via the Haber process.
N2(g) + 3H2(g) ⇌ 2NH3(g)
Reversible reaction is a type of reaction whereby the reaction can proceed in both directions (forward and backward direction).
Dynamic equilibrium is said to be reached in chemical reaction when the rate of forward reaction equals that of the backward reaction and as such, the concentration of the reactants and products remain constant with time even though the movement of substances still occurs between both (reactants and products); while the system shows no further change in properties.
The image below shows the processes that results into dynamic equilibrium:
You can read on chemical properties of matter explained with examples here.
Dynamic equilibrium does not commence at the beginning of a reaction. The forward reaction must first proceed; that is, the reactants collide or react in order to form the products. After some time, the backward reaction also proceeds as the products begins to react, forming back the reactants. This forward and backward reaction continues differentially until the both reactions proceed at the same rate. At this point, dynamic equilibrium is said to be reached.
A reversible reaction must occur in a closed system for dynamic equilibrium to be attained. This ensures that neither the reactants nor products are lost during the chemical reaction. As an instance, iodine is a substance that sublimes (that is; changes directly from solid to a gaseous state when heated).
When iodine is heated in an open container, it sublimes into gaseous iodine which escapes into the atmosphere; and there will be no way for the backward reaction to proceed.
I2(s) -> I2(g)
However, if the heated container was sealed (in a closed system), the iodine crystals sublime into a purple iodine vapour, and both the crystals and vapour remains inside the container until a chemical equilibrium is reached.
Note: The concentrations of both the reactants and products must remain constant and not necessarily the same when dynamic equilibrium is reached in a system.
It is important to state that factors such as 'a change' in concentration, pressure or temperature will affect or alter the dynamic equilibrium in a system. This was explained by a French Chemist named Henry Louis Le Chatelier. It was his principle - 'Le Chatelier’s Principle, also known as the Equilibrium Law' that explains the aformentioned changes, predicting their effects on a system in dynamic or chemical equilibrium.
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Amazing facts in Chemistry
The only letters that failed to appear on the periodic table are letters:
Gold and copper are the only two non-silvery colored metals.
Copper is the only metal that is naturally antibacterial. This is why you would see some children utilize 'copper' water bottles in schools
Water actually freezes faster when it’s warm than when it’s cold
Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy.
If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.
Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre
NOTABLE POINTS IN Chemistry
A major challenge encountered when calculating molecular mass is that it becomes difficult or impossible to calculate especially when the relative molecular mass of large molecules, polymers and macromolecules are involved.
Examples of large molecules (with indefinite molecular masses) include carbohydrates, cellulose and complex sugars.
The large molecules (above) have no specific chemical formula throughout their volume.
Understand that Relative Molecular Mass prove to be useful only when we calculate substances with small and definite molecular sizes. This was proven through the Modifications of Dalton's Atomic Theory.
Calculate the Relative Molecular Mass of Methane (CH4). (Carbon=12.001 and H=1.00794)
Molecular Mass of Methane = 16.033 amu
Calculate the Relative Molecular Mass of Water (H2O). (Oxygen=15.9994 and Hydrogen=1.00794)
Molecular Mass of Water = 18.015 Da
Below are some facts about gold
It is the only metal that has a gold (golden) color.
Gold is present inside the earth crust in all the seven continents.
Pure gold is soft and very stretchable (It can even be stretched into threads).
The Latin name of Gold is aurum which means 'shining dawn'. For this reason, its chemical symbol is 'Au'.
Gold is a very good conductor of electricity. This is why it’s sometimes used in making USB and audio cables.
Gold is non toxic and can be eaten with food. It is sometimes added to desserts in some expensive restaurants.
The term Gold originated from an ancient English word 'geolu' which means yellow.
24karat gold is the purest gold element.
An acid is a substance that produces Hydrogen ions (H+) when dissolved in water (or when in the form of an aqueous solution).
Svante Arrhenius definition of Acid
An acid is a substance that donates a proton in a chemical reaction.
Brønsted Thomas Martin Lowry definition of Acid
An acid is a substance that accept an electron pair in a chemical reaction.
Gilbert Newton Lewis definition of Acid
Finally, Acids can also be also defined as substances that gives out hydronium ion (H3O+) when dissolved in water.
In summary, all acids will always contain the positive H+ (cation) and an anionic group in their formula. For instance, the acid HCl (Hydrogen Chloride) contains H+ as cation and Cl- as its anion.