21 Chemistry -- Foundation and Fundamentals of Chemistry

Is the limestone pure CaCO3? Why is average atomic mass generally fractional?

Is the limestone pure CaCO₃? Why is average atomic mass generally fractional?

1 Answers

# Limestone doesn't exist out in the world as pure calcium carbonate for the most part, and making it into a pure substance usually requires some kind of processing. Mostly, this is us making a distinction between calcium carbonate (the compound) and limestone (the material out in the world).

# The atomic masses of most elements are fractional because they exist as a mixture of isotopes of different masses. Most elements occur as a mixture of isotopes of different masses. The fractional atomic masses arise because of this mixture.

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K yo sab notes bata 11ko entrance exam ma aauxa ra

Entrance should be fully based on the things that you learnt till Class 10 but these days as the competition is increasing some colleges has been found including the questions from class 11 as well like the basic questions which will bridge both 10 and 11. And that's why we saw several students indulging in bridge course classes and all. If you have completed the contents upto class 10 then you can see the notes of 11 class as well it will surely help somehow in entrance. For further more...

How many electrons and neutrons are present in the symbol 2713Al3+?

Atomic no. (Z) = 13 and atomic mass (A) = 27
No. of neutrons = A-Z = 27 - 13 = 14
No. of electrons = 13 - 3 = 10

Al atom loses 3e^- to form Al⁺³.

Define a chemical change and point out its two important characters.

The permanent change in which one compound is transformed into other compound have different properties is known as chemical change.

Two important characters are:

a. It is irreversible change.
b. New compound having different properties are formed.

What information can you obtain from the symbol 3919K?

Atomic no. (Z) = 19 and Atomic mass (A) = 39
No. of neutrons = (A - Z) = (39 - 19) = 20
No. of electrons = Number of protons = Atomic number

What is the formula of methane

CH₄

what is meant by empirical formula of compound is HO?

The empirical formula represents the atomic ratio of HO present in its molecules.

What does chemistry as a science begin with? Define chemistry and matter and also draw flow chart of classification of matter.

Chemistry as a science begins with matter.

Chemistry is a branch of science that basically deals with study of composition and properties of matter and also physical and chemical interaction which may take place among matters.

Matter is anything that possesses mass, occupies space and may be perceived through one or more of our senses.

Flow chart of classification of matter:

Matter

Physical Division

Solid

Liquid

Gas

...

Explain the types of physical division and chemical division of matter.( Also explain the sub-types of chemical division.)

Matter is anything that possesses mass, occupies space and may be perceived through one or more senses.

The physical divisions of matter are:

1. Solid : Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around.

2. Liquid : Liquid matter is made of more loosely packed particles. It will take the shape of its container. Particles can move about within a liquid, but they are packed densely enough that volume is...

Define law, hypothesis and theory. How is the scope and depth of chemistry determined? And list the branches of chemistry and also write the importance of chemistry.

Law : A law is a summarized statement of results obtained by experiments. A law can say what happens but it can't answer why does it happen.

Hypothesis : A hypothesis is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it.

Theory : A theory is a proposed model introduced to establish a relationship between hypothetical causes and experimental observation ( effect).

The scope and depth of chemistry is...

Define atom, according to Dalton's atomic theory. What are atom composed of? Define chemical symbol. Write the symbol of Tin, Lead, Antimony & Platinum with its latin name.

According to Dalton's atomic theory, an atom is defined as the smallest indivisible particle of an element having no free existence in nature.

Atoms are composed of protons, electrons and neutrons.

Chemical symbols are the abbreviations used in chemistry for chemical elements, functional groups and chemical compounds.

Elements with their symbol and latin name are as follow:

ELEMENT	LATIN NAME	SYMBOL
TIN	Stannum	Sn
Lead	Plumbum	Pb
Antimony	Stibium	Sb
...

Define the terms with important points and examples: a).Nucleon b).Atomic number c).Atomic mass number d).Isotopes e).Atomic mass unit(amu) f).Relative atomic mass g).Molecule h).Radical ...

1. Nucleon : A proton or a neutron present in the nucleus of an atom of an element is called nucleon . Example: Carbon consist of 6 protons and 6 neutrons . i.e., there are 12 nucleons in C atom.

2. Atomic Number : The atomic number is the total number of protons present in the atom. Example : the atomic number of sodium is 11. i.e., it contains 11 protons and 11 electrons.

3. Atomic Mass Number : The atomic mass number of an atom is the total number of protons and neutrons (nucleons) present...

i). Naturally occuring neon is 90.9% neon-20, 0.3% neon-21, 8.8% neon-22. Use this figure to calculate relative atomic mass of naturally occuring neon.ii).A natural mixture of hydrogen contains 1H1...

Question no i)Solution:
Given, Naturally occuring neon is 90.9% neon-20, 0.3% neon-21, 8.8% neon-22.
Now, the relative atomic mass of naturally occuring neon = ( mass number of isotope neon-20) x ( abundance%) + ( mass number of isotope neon-21) x (abundance%) + ( mass number of isotope neon-22) x (abundance%)/100%
= [(20x90.9%) + (21x0.3%) + (22x8.8%)] /100%
= (1818% + 6.3% + 193.6% ) /100%
=( 2017.9%) /100%
= 20.179
Question no ii)Solution:
Given, A natural mixture of hydrogen contains ₁H¹ and ₁H^2...

1). Molecular formula of C6H12O6. Calculate a). molecular mass of the compound b).mass ratio and % composition of elements present in the compound2). Empirical formula of glucose is CH2O. Find...

Questions no. 1(a)

Solutions:

Given, Molecular formula of glucose is C₆H₁₂O₆.

Here, Atomic mass of one C inC₆H₁₂O₆= 12 amu

Atomic mass of one H inC₆H₁₂O₆= 1 amu

Atomic mass of one O inC₆H₁₂O₆= 16 amu

Now, molecular mass of the compound = (6*12)+(12*1)+(6*16)=180 units

Question no.1(b).

Solutions:

Given, Molecular formula of glucose isC₆H₁₂O₆.

Here, Mass of C inC₆H₁₂O₆= 6*12 =72

Mass of H inC₆H₁₂O₆=12*2 = 24

Mass of O inC₆H₁₂O₆= 6*16 =96

Now, mass ratio of C:H:O = 72 : 24 : 96 = 3 :1 :...

Write the chemical name and chemical formula of following:Quick limePlaster of parisCaustic sodaCommon saltBlue VitriolWhite vitriolGreen vitriolWashing sodaPotassium ferrocyanidePotassium ferricya...

The chemical name and chemical formula of compounds are as follows:

Compounds	Chemical Name	Chemical Formula
1. Ouick lime	Calcium Oxide	CaO
2. Plaster of Paris	Calcium Sulphate Hemihydrate	CaSO₄.1/2 H₂O
3. Caustic Soda	Sodium Hydroxide	NaOH
4. Common Salt	Sodium Chloride	NaCl
5. Blue vitriol	Copper (II) Sulphate	CuSO₄.5H₂O
6. White vitriol	Zinc Sulphate	ZnSO₄.7H₂O
7. Green vitriol	Iron (II) Sulphate or (Ferrous Sulphate)	FeSO₄.7H₂O
8. Washing Soda	Sodium Carbonate...

Define chemical change with its example. Also define reactants and products. And write general characters of chemical change or chemical reaction. Difference between physical and chemical change.

The changes in which new substance with new chemical properties are formed are called chemical change.

Example: Reaction between washing soda and lemon juice in which CO and other substances are formed.

Original substances participating in a chemical reaction are known as the reactants.

The new substance formed after chemical reaction are known as the products.

The general characteristics of a chemical reaction are :

i). Evolution of gas

ii). Formation of a precipitate

iii). Change in...

Define chemical equation. Why is the burning of wood called chemical change? Mention some significance of chemical equation. What does the formula H2SO4 signify? Explain.

Chemical equations are symbolic representations of chemical reactions in which the reactants and the products are expressed in terms of their respective chemical formulae.

The burning of wood leads to the formation of new substances like ash (carbon), carbon dioxide gas, water vapour, heat and light. This change is irreversible and hence, considered as chemical change.

Some significance of chemical equation are :

1. It explains the specific conditions of temperature,...

State all that is implied by the chemical equation 2H2 + O2 ➡2H2O. Give its limitation and their remedies.

All that is implied by the chemical equation 2H₂ + O₂ 2H₂O are

It explains that on hydrolysis of water we get hydrogenation and oxygen as a product.

# Molecular mass ofH₂=2 g/mol

# Molecular mass ofO₂=32 g/mol

From the balanced chemical equation,

2 2=4 g of hydrogen requires 32 g of Oxygen to react completely.

# Limitations of this equation are

1. It doesn't give the conditions required to carry out chemical equation.

2. It doesn't tell whether heat is absorbed or evolved in the reaction unless the...

Define chemical reaction. Explain its types and sub-types with example.

A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants.

Examples :

i. Combustion

ii. Oxidation (rusting

iii. Decomposition or fermentation

iv. Photosynthesis

v. Reacting acids and bases together.

The different types of chemical reaction are

1.Combination reaction:

In...

How to balance a reaction by Hit and trial method and by Partial equation method. Explain with some examples.

Method 1 :

Hit and Trial Method:

The simplest method to balance a chemical equation is by the hit and trial method. This method is also called trial and error method, or inspection method. In this method, coefficient before the formulae or symbols of the reactants and products are adjusted in such a way that the total number of atoms of each element only both the sides become equal. This is called material balance, or mass balance. In this method first of all, atoms of the element which appears...

Write the qualitative and quantitative significance of symbol. Write an example of redox reaction and justify why the reaction is redox?

Symbols are the short abbreviations used in chemistry for chemical elements, functional groups and chemical compounds.

The qualitative and quantitative significance of symbol are :

1) As each element has its own unique symbol, it can be used to identify the element; moreover, with the use of symbols, the periodic table looks compact and organized. If the name of each element is to be written in the periodic table, then the data will not be organized anymore. Hence, the major qualitative...

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