Topics in ChemistryChemistry 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 Mixtures and Separation of Mixtures Mixtures and Separation of Mixtures - part 2 Mixtures and Separation of Mixtures - part 3
Academic Questions in Chemistry
2NH4+(aq) + Ag+(aq) -> 2H4AgN
The equation above represents _____ acid.
A. Svante Arrhenius'
C. Gilbert Lewis'
E. Sir Isaac Newton's
F. Albert Einstein's
According to Brønsted Thomas Martin Lowry, an acid is defined as _____.
A. Any substance that produces hydrogen ion (H+) when dissolved in water
B. A substance that accepts electron pair in a chemical reaction
C. A substance that gives out hydronium ion (H3O+) when dissolved in water
D. A substance that donates a proton in a chemical reaction
E. A substance that reacts with a base to form salt and water
F. A substance whose hydrogen ions (H+) are displaced after a reaction with metals higher in the activity, reactivity or electrochemical series
Which of the following is NOT a characteristic of chemical change?
Which of the following statement is FALSE concerning a physical change _____.
The following substances will sublime EXCEPT _____.
Which of the following is a state of matter?
The ideal way of separating a mixture of blood is through _____.
Which of the following separation technique is used to separate an insoluble solid that sediments in a liquid?
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To get a better understanding of the behaviors of electrolytes (during electrolysis), we need to first understand what ions are. The reason is because electrolysis involves the behavior ions in solution.
Simply put, ions are charged atoms.
This implies that ions are formed from atoms.
It is important we know what valence electrons are before we proceed on ions. The instance below summarizes what valence electrons are:
Valence electron(s) is defined as the number of electron(s) in the outermost shell of an atom.
The group one elements (in the periodic table) have got 1 valence electron and will undergo chemical reaction by donating it out to attain an octet or duplet configuration.
Note: Group 1 elements have got one valence electrons, group 2 have got two, group 3 has three and it follows in that pattern through group 7. However, group 8 have got eight valence electrons, except for helium which has two.
The image below shows the chemical reaction between sodium atom, (a group 1 element) and chlorine atom, (a group 7 element):
Regarding elements with 1 valence electron, it will require lesser energy to give out its 1 electron towards attaining stability (octet configuration) rather that accepting 7 electrons.
In fact, no element in the periodic table will donate or give out 7 electrons to begin with.
Note: Chemical stability is achieved when an element has 8 electrons in it's outermost shell (called octet configuration). In Hydrogen and Helium atoms, chemical stability is achieved when they have 2 electrons (called duplet configuration).
A positively charged ion is called a cation and it's formed when an atom donates electron(s) in chemical reactions.
Sodium atom (Na) will give out its 1 valence electron to form sodium ion (Na+). Please see the diagram above.
Conversely, group seven elements (of the periodic table) have 7 valence electrons and will undergo a chemical reaction by accepting one electron to attain an octet configuration.
A negatively charged ion or anion is formed whenever an atom accepts electron(s).
Chlorine atom (Cl) will accept 1 electron from a group 1 element (e.g sodium) to for chlorine ion (Cl-).
Note: An octet or duplet configuration is a state whereby atoms or ions have the maximum of eight or two valence electrons. They are stable as a result and do not need further reaction with any other element.
In short, all elements undergo chemical reaction in order to attain the octet or duplet configuration.
If the attainment of an octet or a duplet configuration is achieved via the transfer of electrons, then an ion will be formed.
Chemical reactions or bonds that involves the transfer of electrons are termed ionic or electrovalent bond.
We have 2 types of ions. They are:
A cation is a positively charged ion. Examples are Na+, H+, K+, Mg2+, Ca2+ and so on. They will move to the negative electrode during electrolysis.
The negative electrode in electrolysis is referred to as the Cathode. Therefore, the cations migrate to the cathode in electrolysis.
An anion is a negatively charged ion. Examples are Cl-, F-, O2- and OH-. They will move to the positive electrode during electrolysis.
The positive electrode in electrolysis is referred to as the Anode. Therefore, the anions migrate to the anode during electrolysis.
Electrolytes are defined as solutions or molten compounds or paste like compounds that conduct electricity. Examples are brine (a concentrated solution of sodium chloride) and calcium hydroxide or Ca(OH)2.
The image below shows the process of electrolysis. The electrolyte is composed of ions (cations and anions) which will eventually migrate towards their respective electrodes. You can read more on electrodes here.
Electrolytes are composed of ions. The ions that makes up an electrolyte are always dissociated during electrolysis.
Note: Solids that conducts electricity are called conductors.
During the process of electrolysis, electrolytes will dissociate into its constituent ions; and will migrate to their respective electrodes when an electric current is passed through it. This process of dissociation is summarized in the ionic theory.
The strength of dissociations of the ions present in an electrolyte will determine whether the electrolyte is strong or weak.
We have 2 types of electrolytes. These are:
1. Strong electrolyte: They dissociate completely into their constituent ions when electricity is passed through them.
Example of strong electrolyte are KCl(aq) (potassium chloride) and Ca(OH)2(aq) (calcium hydroxide).
2.Weak electrolyte: They dissociate partially into their constituent ions when electricity is passed through them.
Examples of weak electrolytes are Ethanoic acid (CH3COOH) and Mercury chloride (HgCl)
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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. Please read some interesting facts about gold here
Copper is the only metal that is naturally antibacterial. This is why you would see some children carry copper water bottles to school
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.
Please read on modification of Dalton's atomic theory here.
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