Questions on Chemistry
The first problem for all of us, men and women, is not to learn, but to unlearn - Gloria Steinem
The act of unlearning is an excellent form of learning. Infact, you will need the skills of unlearning if you intend to become an expert in your desired field.
Do yourself a favor by unlearning, learning and re-learning on a daily basis
If you don't design your own life plan, chances are you'll fall into someone else's plan. And guess what they have planned for you? Not much - Jim Rohn
There's something special about you. It doesn't matter whether you work for a company or someone; what matters is the amount of investment you've made on yourself.
Investing in yourself is the best life plan you can design for your future
Peace begins with a smile - Mother Teresa
Never underestimate the power of your smile. It can lift up the depressed, improve the mood of the downtrodden and even discourage a suicidal attack. Also remember that your smile makes you more beautiful
Smile always for your own good and the good of others
The only person who is educated is the one who has learned how to learn …and change - Carl Rogers
To perfect your learning process, you must learn, unlearn and re-learn. Infact, we all need to learn how to unlearn those vices we know about ourselves.
Do you know that seeing the devastating consequences of vices (perhaps in movies or real-life) can initiate the unlearning processes in one who does such?
Start where you are. Use what you have. Do what you can - Arthur Ashe
Start now. You've got all it takes to achieve greatness, so no environment can limit you. Just begin something, give in your best and don't stop.
Remember, don't stop giving your best if you truly desire greatness. Nothing can stop you except yourself
The _____ spectrometry experiment conducted on isotopic elements gave a confirmation for the existence of isotopes.
D. Number of moles
F. Amount of substance
Isotopes are defined as elements having the same number of protons (atomic number) but different number of neutrons. In summary, isotopes (or isotopic elements) have got the same atomic number but different mass number.
The existence of isotopes was eventually confirmed after the mass spectrometry experiment was conducted on isotopic atoms.
Some elements exhibiting isotopy include:
3517Cl and 3717Cl : Isotopes of Chlorine with mass numbers 35 and 37 respectively.
11H (Hydrogen) and 21H (Deuterium) and 31H (Tritium) are isotopes of hydrogen with mass numbers - 1, 2 and 3 respectively.
John Dalton's first atomic theory was modified based on a discovery made by _____.
A. Sir Isaac Newton
B. Albert Einstein
E. Boyle and Charles
F. Gay Lussac
Dalton's first atomic theory states that:
All matter consists of tiny indivisible particles called atoms.
The above theory was modified based on a discovery made by Rutherford.
According to Rutherford, atoms can no longer be regarded as indivisible because they can be divided into the followings:
Which of the following isn't an element of the periodic table.
J is not an element of the periodic table. Infact, it is the only letter not present in the periodic table.
The names of the elements (from the options in the questions) are listed below:
Y - Yttrium
W - Tungsten or Wolfram
B - Boron
U - Uranium
K - Potassium
Below is an image of the periodic table containing all elements.
According to the periodic table, elements in the same group have got the same number of shells.
As we go down the groups of the periodic table, the shells of each element increases by one. As an instance, hydrogen, sodium and potassium are group one elements. However, each has got one, two and three shells respectively.
It is noteworthy to state that all elements in the same group have got the same number of valence electrons, (not shells). Understand that valence electrons are the electrons present on the outermost shell of an atom. As an instance, all group one elements have got one valence electron.
The image below shows the electronic configuration of sodium, a group one element with one valence electron.
The periodic table of elements is also called the Mendeleev's table.
The periodic table, also called the periodic table of elements or Mendeleev's table is a table that shows an organized arrangement of the 118 elements according to their atomic number.
The periodic table is also called Mendeleev's table in honor of its creator, Dmitri Ivanovich Mendeleev, a Russian chemist and inventor. He is famously remembered for creating the periodic table of elements and formulating the periodic law.
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
ANSWER: Emperical formula
The emperical formula of a compound is defined as that which shows only the relative number of atoms of each element present in a compound.
Understand that the emperical formula of a compound is always the simplest formula of such compound and is derived from experimental data and analysis.
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)
Step 1: Identify the given parameter from the question.
Fe = 69.94%, O = 30.06%.
Empirical formula = Fe?O?
Step 2: Convert the percentages to gram. (just attribute grams to the %).
69.94% = 69.94g while 30.06% = 30.06g
Step 3: To get the mole ratio of each element, convert the gram to moles using the formula (mole = mass/molarmass). Please merorize this formula because we always work with moles in Emperical Formula.
Mole of Fe: 69.94/55.85 = 1.252mol
Mole of O: 30.06/16 = 1.879mol
Step 4: Divide both sides by the smallest mole ratio.
Iron has the smallest mole ratio in our case, therefore: 1.252/1.252 = 1, 1.879/1.252 = 1.5
We now have the formula = Fe1O1.5
Step 5: Multiply each of the moles by the smallest whole number that will convert each into a whole number. (In our case, the number '2' is the smallest whole number that will make '1.5' and '1' whole numbers when multiplied by it.
For iron (Fe), we will have 1 x 2 = 2
For oxygen (O), we will have 1.5 x 2 = 3
Step 6: Write the empirical formula.
The empirical formula= Fe2O3
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
ANSWER: Benzene ring has a carbon-carbon triple bond in its structure
Benzene is an aromatic hydrocarbon. It has a carbon-carbon double bond in its structure. See the image below.
The ability of carbon to form long chain of itself is called _____.
A. Carbon chain reaction
E. Organic chemistry
F. Carbon moleculation
Carbon is the focus of organic chemistry. This is true because it can form long chain of itself and this process is called catenation.
Understand that organic chemistry is the study of carbon and its compounds. Carbon is the focus because of its ability to catenate.
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
ANSWER: 16.033 amu
To answer the question correctly, you need to know the chemical formula for methane which is CH4.
With this knowledge, we can correctly add the values in accordance to their mole(s). That is:
12.001 + (1.00794 x 4)
Note: amu stands for Atomic Mass Unit. Dalton (Da) is also a unit for relative molecular mass
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
ANSWER: It is the 50th rarest metal amongst all elements found beneath the earth crust
Gold is the 58th rarest metal amongst all elements found beneath the earth crust.
Which of the following is not an example of a chemical change?
ANSWER: The melting of candle wax
The melting of candle wax is a physical change and not a chemical change.
In a chemical change, a new substance is formed and whatever substance is formed can't be reversed to what formed it.
When candle melts, the composition of substances in the melted candle is still the same as that of original candle. The only difference is that it changed its state from solid to liquid. If left to cool for some time, the liquid candle wax will change its state back to solid. For this reason, both the solid candle and the melted candle wax will have the same composition and chemical formula.
A similar process happens when water is put in a freezer. The liquid water only changes its physical state to solid water (ice) but its composition and chemical formula remains the same (H2O).
Note: The melting of candle is a physical change while the burning of candle is a chemical change.
Which of the following is not a fraction of crude oil?
Fractions of crude oil are the various products obtained after crude oil (or petroleum) is separated via fractional distillation.
The fractions are listed below. (From the most volatile to the least volatile):
Fuel Gas (Most Volatile)
Bitumen (Least Volatile)
The Separating Funnel is a technique used in the separation of mixtures. Another name for Separating Funnel is the _____ Funnel.
Separating Funnel, also called Separatory Funnel is used to separate a mixture of two immiscible liquid.
An example of a mixture of two immiscible liquid is water and oil.
The water (which is denser) remains at the bottom while the oil floats on it.
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
Answer: Gilbert Lewis Acid
Notice from the equation that silver ion (Ag+) accepts a pair of electron (2 electrons or 2H+) from 2 moles ammonium molecule (2NH4+) to form ammonium silver (2H4AgN).
The fact that silver ion (Ag+) accepts a pair of electron from ammonium qualifies it as a Lewis acid. In short, any substance that accepts a pair of hydrogen ion (2H+), which is equivalent to 2 electrons is a Lewis Acid.
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
Answer: A substance that donates a proton in a chemical reaction
Option A definition of an acid was made by Svante Arrhenius
Option B definition of an acid was made by Gilbert Newton Lewis
Option C is a definition generally associated with acids
Options E and F has to do more with the properties of acids
Which of the following is not a characteristic of chemical change?
ANSWER: Blood is an example of a chemical change
A chemical change is a change that is NOT easily reversible and a new substance is formed.
Note: Blood is an example of a physical change. In fact, blood is a mixture and can be separated via an appropriate separation technique.
Below is an instance of a chemical change:
When an iron begins to decompose (rust), a new substance called rust is formed. Rust is (brownish) in color with the chemical formula Fe2O3. It is important to understand that rust is not iron (Fe).
Rust is an entirely new substance and it is the product of a chemical change that results when iron is exposed to air and water.
In short, rust results from the oxidation of iron.
Which of the following statement is false concerning a physical change _____.
ANSWER: Substances formed in a physical change have a unique chemical formula and IUPAC name
A physical change is a change that is easily reversible and no new substance is formed.
The substances formed in a physical change does not have a unique chemical formula or IUPAC name.
For instance, a mixture of salt and water is a physical change. The substance formed will simply be referred to as a salt solution. Salt solution has no specific chemical formula.
In another instance, a mixture of sand and stone is a physical change. Sand and stone does not have a chemical name and formula. (It's simply called a mixture of sand and stone).
The following substances will sublime EXCEPT _____.
ANSWER: Sodium Cryolite
Sodium Cryolite does not sublime
A substance is said to sublime when it changes directly from solid to gas OR from gas to solid without passing through the liquid phase.
Note: When we have a mixture of two solids where one sublimes, such a mixture can be separated through a separation technique termed Sublimation.
To separate a mixture via sublimation, all we need do is to heat both substances in a container. The solid that sublime is collected in its gaseous form while the other solid (that doesn't sublime) may melt in the container.
Which of the following is a state of matter?
Matter can be defined as anything that has mass and occupy space. It exists in 4 states. These are:
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Chemistry topicsLe 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
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