Class 9 Chemistry
1st Chapter Important Short Questions
What do moles mean in chemistry?
In chemistry, a mole, sometimes spelled mol, is a standard scientific unit for measuring huge amounts of very small entities like atoms, molecules, and other defined particles.
or
A mole is the mass of a substance that contains 6.023 x 1023 particles of that substance.
The mole is the SI unit used to measure the amount of substances.
one mole of carbon-12 has 6,022 x 1023 carbon atoms and weighs 12 grams.
Compare the gram atomic mass, the gram molecular mass, and the gram formula mass.
In contrast to the gram formula mass, which denotes one mole of ionic formula units of a compound, the gram atomic mass represents one mole of atoms of an element. Gram molecular mass signifies one mole of molecules in a molecular state of a chemical or element.
2. Gram atomic mass comprises 6.022 x 1023 atoms, gram molecular mass comprises 6.022 x 1023 molecules, and gram formula mass comprises 6.022 x 1023 formula units.
Therefore, one mole can be defined as gram of formula mass, atomic mass, or molecular mass.
Which branch of chemistry studies the behaviour of gases and liquids?
Physical chemistry is the discipline of chemistry that studies the properties of gases and liquids.
Which field of chemistry deals with the energy of atoms and its practical applications?
Nuclear chemistry is concerned with atomic energy and its practical applications.
What applications can Nuclear Chemistry serve?
It has extensive applications in medical treatment, food preservation, and the production of electricity via nuclear reactors.
Which branch of chemistry is concerned with the manufacture of paints and papers?
Industrial chemistry is concerned with the manufacture of paints and papers.
What applications does Inorganic Chemistry have?
It is applicable to all aspects of the chemical industry, including glass, cement, ceramics, and metalworking.
Name one solid, one liquid and one gaseous element present at room temperature.
Sodium and Iron are solid elements, while Bromine and Mercury are liquids. Gas: Oxygen , Nitrogen, and Chlorine
How can it be defended that air is a homogenous mixture? What compounds are found in it?
Air is a physical mixture of substances such as nitrogen, oxygen, carbon dioxide, noble gases, and moisture, and its composition is consistent throughout. So, the combination is homogenous.
Determine the mass of three moles of atoms of oxygen.
There are 3 x 16 = 48 g of oxygen in 3 moles.
1 mole of Oxygen and 1 mole of Sulfur have the same mass.
No, 1 mole of oxygen and 1 mole of sulphur atoms do not have the same mass.
What is the difference between one atom of carbon and one gram atom of carbon?
The atomic mass of a single carbon atom is 12 amu. However, when this mass is given in grams, it is referred to as the gram atomic mass. 1 gram of carbon equals 12.0 g.
Provide the composition of the Earth Crust in terms of the three most abundant elements.
The Earth’s Crust is composed of three primary elements in the following proportions. Oxygen 47% Silicon 28% Aluminum 7.8%
Why atomic mass of an atom is defined as relative atomic mass?
Atomic mass is described as relative atomic mass, since it is the mass that compares or relates to 1/12th of the mass of the carbon 12 isotope.
Is atomic mass unit a SI unit of an atomic mass?
Yes, the SI unit of atomic mass is the atomic mass unit.
Define the term “industrial chemistry.”
This discipline of chemistry relates to industrial processes, as stated in Industrial Chemistry. It involves the study of properties’ applications and the implementation of procedures for the preparation of large-scale industrial sales.
What is the definition of relative atomic mass?
“The relative atomic mass of an element is the average mass of its atoms as a compound compared to one-twelfth the mass of a single Carbon-12 atom. Example: Na has a mass of 23 amu .
When atomic mass unit is expressed in grams, it is. 1 amu = 1.60×10-24 g
What is the relationship between the atomic number and the atomic mass?
The following describes the relationship between atomic number and atomic mass.
A = Z + n
Where
A = mass number
Z = Atomic number
n= no of neutrons
Based on their properties, elements are classified into which groups?
Based on their properties, elements are classified as metals, non-metals, and metalloids.
Define atomic mass unit. Why is it essential?
Atomic Mass Unit: The atomic mass unit is the unit for relative atomic masses. Its symbol is the amu. One atomic mass unit is one-twelfth the mass of one carbon atom and one-twelfth the mass of one carbon-12 atom. 1 amu is equivalent to 1.66 x 10-24 g when expressed in grams.
What is Chemistry?
Chemistry is the branch of science that studies the composition, structure, properties, and reactions of matter.
What is the significance of an element’s symbol?
Significance of an element’s symbol :
It takes less time to save time and the element may be identified by that symbol over the globe. For example oxygen(O),sulphur(S), Nitrogen(N)
Define empirical formula and provide examples.
It is the most simple whole-number ratio of atoms contained in a compound. CH is the empirical formula for benzene (C6H6). HO is the empirical formula for hydrogen peroxide (H2O2).
How is the atomic number defined and represented?
“The atomic number of an element is equal to the number of protons in its atoms’ nuclei.” Representation: “Z” represents it.
Which term is used to describe the mass of one mole of molecules of a substance?
Gram molecular mass
How many atoms are there in one gram atomic mass of a substance?
The number of atoms in One gram atomic mass of a substance is equivalent to Avogadro’s number, which is 6.023 x 1023.
What does valency mean?
Valency is the capacity of an element to combine with other elements. For example. The valency of carbon is four.
What does variable valency mean?
Some elements show more than one combining power, which is known as variable valency. For example, the valency of iron in ferrous sulphate is 2, whereas in ferric sulphate it is 3.
Define Biochemistry.
“The study of the structure, composition, and chemical reactions of substances present in living organisms.
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