Chemistry
what is the difference between mechanical and chemical digestion ?
Mechanical digestion :- In this type of digestion the food is broken down into simple particles in mechanical way , like chewing in mouth by teeth and churning of food in stomach by the muscular movements of the smooth muscles of stomach walls. Chemical digestion :- In this type of digestion the complex molecules of
Explain how vacancies are introduced in an ionic solid when a cation of higher valency is added as an impurity in it.
In case of ionic solids the opposite ions balance the charge of each other. The amount of cations and anions is mostly same in case of charge. But when we add a cation with higher charge , the cation can replace the other cations in lattice and can create vacancy because to balance the charge,
A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong ?
These type of semiconductors have excess electrons present in the lattice that are responsible for the conduction. These are formed when the group 14 elements like Silicon are doped with group 15 elements like P and As. The group 14 elements have 4 valence electrons and group 15 elements have 5 valence electrons . One
Ionic solids , which have anionic vacancies due to metal excess defect , develop colour. Explain with the help of a suitable example.
When we add extra metal to the lattice, it provide extra electrons to the lattice and the anions of the lattice leave their lattice points . These vacant sites are occupied by the electrons. And the free electron can easily absorb energy and can jump to higher level. As these energy transitions are in visible
What type of stoichiometric defect is shown by (i) ZnS (ii)AgBr.
(i) ZnS have large difference in the size of their ions and due to this it shows Frankel defect. (ii) AgBr shows Schottky defect and Frankel defect.
Which of the following lattice has the highest packing efficiency? (i) simple cubic (ii) bodycentred (iii) hexagonal close packing.
Packing efficiency of all these kind of arrangements is given as follows. (i) Simple cubic :- Its packing efficiency is 52% . (ii) Body centred cubic :- Its packing efficiency is 68%. (iii) Hexagonal close packing:- Its packing efficiency is 74% . Conclusion :- From the above data we can conclude that hexagonal close packed
What is the two dimensional co-ordination number of a molecule in square close packed layer ?
In a square close packed two dimensional layer , four other particles touch one particle. Thus its coordination number is 4 .
What type of defect can arise when a solid is heated ? Which physical property is affected by it and in what way ?
On heating the crystal lattice, some of the lattice particles gain enough energy that they jump from their lattice points. Due this the crystal appears coloured and its density decreases.
Give the siginificance of lattice point .
These are the points in a crystal lattice that can be occupied by an atom, ion or a molecule.
Why are solids rigid ?
In case of solids the particles have strong forces of attractions between them . Due to this they can not move or change their positions. Due to this they are rigid.
How we can calculate the number of electrons in a given shell ? K L M N
We can calculate the number of electrons in a given shell by using a simple formula as given below. 2n² Where “n” is the number of shell. For example In case of K shell , n=1 So the number of electrons = 2n² = 2 x 1² =2 So in K shell we have 2
How we can distinguish between hexagonal and monoclinic unit cells ?
In case of Hexagonal unit cell we have two sides equal , and two angles equal to 90 degrees(right angles) but the third angle is of 120 degrees. a = b ≠ c, and similarly α = β = 90 ̊, ɣ = 120 ̊ But in case of monoclinic unit cell we have unequal sides but
What is rancidity ? Why the packets of chips and fries are flushed or filled with nitrogen gas while packing?
It is the foul smell produced by the oxidation of oils and nuts. Mostly the bitter taste of peanut and food made by frying is due to rancidity . Normally the oily substances which are not covered properly , react with the oxygen of air and get oxidised thus give a foul smell. Removal of
Why should a magnesium ribbon should be cleaned before burning in air?
Magnesium is a reactive metal, it reacts with the oxygen of air and forms magnesium oxide. Magnesium oxide makes a layer on the upper surface of the metal. Which makes it difficult for the magnesium to get burnt and give characteristic flame. By using sandpaper we can remove its upper layer for proper combustion reaction
what is the chemical formula for photosynthesis ?
Actually it is a process in which the green plants synthesize their food from the water and carbondioxide in the presence of sunlight and chloroplast. The following reaction depicts the chemical change during photosynthesis.
what kind of substance are alloys ?
Today we are in a modern era where a lot modernisation has took place. In the field of metals various metals are mixed to get the desired properties. The alloys are used in transportations , machines , telecommunications and a lot more. Basically the alloy is the homogenous mixture two or more metals and some
How the atomic size changes when we move from left to right in a period in modern periodic table ?
The atomic Size is an important property that governs various behaviours of an atom or an element, like valency , electronegativity and metallic character. when we move from left to right the nuclear charge increases at every increase of atomic number. Due to increase in nuclear charge the electrons are attracted towards nucleus with more
is burning a chemical change ?
Yes it is a chemical change as it involves the formation of ash and releases heat. Which can not be reversed to get fuel. In a chemical change the change of properties take place . For example we can write on paper and can fold it ,but if we burn it we get ash and
is density a physical or chemical property ?
Density depends upon the number of particles in a unit area. So it doesn’t matter what kind of particles are used. So it is a physical property.
is dissolving a chemical change?
No, dissolving is a physical process, provided that the substances which are being mixed should not react with each other.
how to name chemical compounds ?
Naming the chemical compounds take a lot of practice and memorising some rules just click here .
How is HCl, an extremely potent acid, formed in our stomach and how does it not react with our organs?
This is true that a strong acid HCl is formed in our stomach , but it does not harm the internal tissues or organs. The acid is formed for two major reasons. To carry out the digestion especially the enzyme pepsin requires acidic medium for the proper functioning . The acid acts as a first
What is the outermost electronic configuration of the vanadium ?
Vanadium’s electronic configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d3 the outer shell configuration is 4s2 3d3
Which specie can act as what are lewis base s ?
Any atom , ion, complex ion, or group of atoms that can donate a pair of electrons are the Lewis bases. for example ammonia(NH3 ) , hydroxide ion(OH – ), chloride ion (Cl – )
how did mendeleev arrange chemical elements ?
Mandleev arranged the elements on the basis of increasing order of the atomic masses of the elements. He divided the 63 elements which were known or discovered at that time. There were 8 groups and 6 periods in his Periodic Table. Most importantly he made cards of every element , and wrote the reactions of
Is it compulsory to read periodic classification of elements before chemical bonding or Can I start chemical bonding before periodic classification?
Actually chemical bonding is based on the Atomic number and electronic configuration. And the main thing is valency which is based on the number of outer(valence) electrons. Valency decides that how many bonds can be made by an atom . Thus if you ignore periodic table, you have to learn atomic number and electronic configuration
The electrons that gain enthalpy for metals is positive and negative for non metals. Also, if metals are bigger in size than non metals then, how can electrons gain enthalpy is inversely proportional to the atomic size?
The answer is simple, like you are hungry you can pay more to get the food than that of the person who is less hungry, Similarily here the non metals want electrons thus they spend the energy more , or they release the energy. By this they lose the energy. So smaller is the size
Is rusting a chemical change ?
Chemical change is a change in which a new substance is formed which is have totally new properties . And during rusting of iron, the iron oxide is formed that will not show the shine of metal, will not be a good conductor of electricity etc. thus rusting is a chemical change.
Which element has the highest ionization energy in the 3rd period?
Ar, Argon is having the highest ionisation energy in 3rd period. This is due to the fact that it belongs to noble gases , and their outer shell is complete and they are enough stable. So to bring out the electron by applying energy is not an easy task.
Why is the more covalent character, the less the melting point?
The covalent compounds have low melting and boiling points. There is a reason behind this phenomenon. In case of covalent compounds the molecules are non-polar and even if there is a polarity in the molecule, that is also just for a moment. Thus each molecule exists as a discrete particle which do not have affinity
how do enzymes catalyze chemical reactions ?
The enzymes increase the surface area and makes it available for reactants to come closer and react. Thus this makes it easy for the reactants to react faster and thus the rate of chemical reaction increses.
how is the chemical symbol of an element determined ?
To determine the chemical symbol of an element we follow 2 main rules given below :- 1. The symbol of every element is expressed with capital letter. 2. If symbol includes more than one alphabet , then the first alphabet will be in capital case and second will be in lower case.
what happens to atoms in a chemical reaction ?
During a chemical change or chemical reaction , the new substances are formed with different properties. But, The atoms remain unchanged during a chemical reaction. Only their rearrangement takes place. As shown below :- 3Fe(s) + 4 H2O(l) ——–> Fe3O4 (s) + 4 H2(g)
Which will cause more burning , liquid water at 100°C or steam at 100°Celcius.
The steam will cause more burning . This is due to the fact that water absorbs heat at 100°C to make steam or transform into gas , but the temprature remains the same. So the heat provided is utilized in changing the state. Thus stem is having more (hidden) heat even if its temperature is
is burning wood a chemical change ?
Yes burning of wood is a chemical change as it leads to the formation of a new substance ash, which is chemically different from the wood. The chemical properties of ash are totally different from that of the wood.
what is a balanced chemical equation ?
A balanced chemical equation is the equation that is having equal number of atoms on both of the sides, that is on reactants side (Left Hand Side) and products side (Right Hand Side). Here in the following reaction we can see clearly 3Fe(s) + 4 H2O(l) ——–> Fe3O4 (s) + 4 H2(g) For further clarification just click on
Is melting of ice a chemical change ?
No , melting of ice will not be a chemical change as it simply involves the change in the state of water. But during this change the colour, odour, taste , chemical or molecular formula will remain the same . And these all are the indications of physical change only.
What are the chemical changes ?
The detailed simplified and shortest differences and explanation is given in the following link just have a look. https://theunconditionalguru.in/2020/04/19/what-are-some-basics-of-chemical-reactions-and-chemical-equations-how-we-can-learn-the-chapter-1-one-cbse-pseb/
how do you balance chemical equations ?
The complete steps to balance the chemical equation is given here with example https://theunconditionalguru.in/2020/04/19/how-we-can-to-balance-the-chemical-equation-cbse-class-10-pseb/
what is a chemical indicator ? And give its types.
Chemical indicators are the substances that give us the information about acids and bases by changing their own colour or smell. types of indicators :- Natural indicators :- These are the indicators that we get from the nature and are used as it is. For example :- Litmus and turmeric . Synthetic indicators :- These
what is the chemical formula for baking soda ?
The chemical formula of baking soda is NaHCO3, and its name is sodium hydrogen carbonate.
what is the chemical formula for calcium carbonate ?
CaCO3 is the chemical formula of calcium carbonate.
why do most atoms form chemical bonds ?
Kossel and Lewis in 1916 Developed the theory for the bond formation after watching the behavior of noble gases. The noble gases were inert in behavior and do not react with any substance. Kossel and Lewis found that the Octateof noble gases was complete so they do not react. They gave the theory that the
How is energy involved in chemical and physical changes ?
Physical and chemical changes are associated with energy changes. For this we have to understand the type of changes. 1. Exothermic :- These are the changes that release energy when they occur . 2. Endothermic :- The changes that occur by absorbing the energy are the endothermic . In case of chemical change the reaction
How do catalysts increase the rate of a chemical reaction ?
The catalyst is a substance that increase the rate of reaction without getting consumed in a chemical reaction. It is recovered as it is after the reaction. The catalyst increase the rate of reaction by following two ways :- 1. The catalyst provide the surface area for the reactants to react easily. 2. The catalyst
During dilution why acid is added to water not water added to the acid ?
The precautions must be taken while dilution. And it has to be taken care of that it is to be done only by the experts. We have to be strict and stick to the statement , ” Always add acid to water while dilution”. The dilution of acid is a highly exothermic process . Now
What is the chemical name of the compound cu2co3 ?
The chemical name of Cu2CO3 is Copper(II) carbonate and it is also named as Cupiric carbonate .
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