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No. of moles=given mass/molar mass =48/4=12 mole The molar mass of He is 4 g which is usually twice the atomic number and the atomic no. of He is 2 so 2*2=4

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Vedika Kengale 3 years, 8 months ago

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Ankush Ranjan 3 years, 8 months ago

C) 12

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In annual examOnly ncert question answers paper mein ayenge or notes and exemplar bhi ayenge

Posted by Himanshu Shukla 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Aman Meena 3 years, 8 months ago

What is pure substance

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Is Newton's law is valid only in earth of everywhere

Posted by Shriram J 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Ritika Prasad 3 years, 8 months ago

It is valid everywhere

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Shriram J 3 years, 8 months ago

Hii to all answer to my this question

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A 0.24g sample of compound of oxygen and boron was found by analysis to contain 0.096g of boron and 0.144g of oxygen. Calculate the percentage of composition of tthe compounded by weight

Posted by Ayushman Kashyap 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Parul Ailawadi 3 years, 8 months ago

Composition of Boron=( 0.096/0.24)×100= 40% Composition of Oxygen=( 0.144/0.24)×100= 60%

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What is homogeneus

Posted by Varshini Varshini 3 years, 8 months ago

CBSE > Class 09 > Science

3 answers

Abhishek Kumar 3 years, 8 months ago

The mixture which is mixed with uniform composition throughout their mass is called homogeneous mixture

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Kripa Daga 3 years, 8 months ago

A mixture which has uniform composition throughout is known as homogeneous

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Jiya Patel 3 years, 8 months ago

A mixture which has a single phase is called homogeneous mixture.

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What is meant by a "Substance" ?

Posted by Priyal Gupta 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

☆ Pranal Rewatkar ☆ 3 years, 8 months ago

A SUBSTANCE IS A PURE SINGLE FORM OF MATTER

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The speed of bicycle decreases from 18 to 9 km/h. If the total mass of the cyclist including the bicycle is 70 kg. Calculate the work done in overcoming the friction offered by the brake and the road. Does the K.E. of the system also reduce to half its initial velocity?

Posted by Rohan Sinha 3 years, 4 months ago

CBSE > Class 09 > Science

1 answers

Sia ? 3 years, 4 months ago

m = 70 kg
v = 9 kmph = 9 * 5/18 = 2.5 m/s
u = 18 kmph = 18 * 5/18 = 5 m/s
Work done = change in kinetic energy
= initial KE - final KE
= 1/2 m u² - 1/2 m v²
= 1/2 * 70 * 5² - 1/2 * 70 * 2.5²
= 875 J - 218.75 J = 656.25 J
The speed has come down to half its value. But the Kinetic energy becomes 218.75/875 = 1/4 th of inital KE.

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are ribosomes a cell organelle

Posted by Mehul Jain 3 years, 8 months ago

CBSE > Class 09 > Science

4 answers

Sanjana Parmar 3 years, 8 months ago

Yes

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Shriram J 3 years, 8 months ago

Yes absolutely it is a cell organelles as it produce proteins

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Priyal Gupta 3 years, 8 months ago

Yes ribosomes are a cell organelle. They are attached to the rough endoplasmic reticulum in the cell

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Bagadhi Tanuj Chowdary 3 years, 8 months ago

Yes

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What is phloem parenchyma

Posted by Smit Pandya 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Rimjhim Goswami 3 years, 8 months ago

Phloem parenchyma is one of the types of phloem cells it help in food storage

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Ayush Garg 3 years, 8 months ago

It's a part of phloem which is a part of animals tissue

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Ozone is the example of

Posted by Nisha Murali 3 years, 8 months ago

CBSE > Class 09 > Science

5 answers

Sanjana Parmar 3 years, 8 months ago

Triatomic molecule

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Tejash Jha 3 years, 8 months ago

Triatomic

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Saloni Harinkhede 3 years, 8 months ago

Triatomic

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Kalash Tulsi Pareek 3 years, 8 months ago

Triatomic

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Priyash Raj 3 years, 8 months ago

Triatomic

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How can you derive speed from a distant time graph ?

Posted by Hasina Mandar 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Priyash Raj 3 years, 8 months ago

Yes

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Derive the formula of Number of particles after defining mole concept.

Posted by Manvendra Parmar 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Priyash Raj 3 years, 8 months ago

No. Of molecule = no. Of mole × Avagardo Constant

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Define force and momentum ?

Posted by Khusi Pradhan 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Akash Kumar 3 years, 8 months ago

A push and pull an object is called force AND The product of mass and velocity of an object is called momentum

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Compute the mathematical formula of calculating potential energy

Posted by Jagyaseni Behera 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Baalveer Returns 3 years, 8 months ago

M×G×H where m is mass g is gravitational force h is height

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Priyash Raj 3 years, 8 months ago

P. E = M×G×H where m is mass g is gravitational force h is height

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Joseph jog from one and a to other b of a straight 300m road in 2min 30s and then

Posted by Nihal Rajak 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Mohit Tanwar 3 years, 8 months ago

Its depends on Joseph

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Anushk Ramesh 3 years, 8 months ago

Yo bro

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Why does protons of a atom doesn't repel each other like alfa rays repels the nucleus

Posted by Utkarsh Chaturvedi 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Saloni Harinkhede 3 years, 8 months ago

Because the simlar charge reepal each other

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Priyash Raj 3 years, 8 months ago

Because the simlar charge reepal each other

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experiment on physics calculation of least count

Posted by Asma Raza 3 years, 8 months ago

CBSE > Class 09 > Science

0 answers

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Name two air borne diseasr

Posted by Abhijeet Tiwari 3 years, 8 months ago

CBSE > Class 09 > Science

4 answers

Ankush Ranjan 3 years, 8 months ago

Asthama, chicken pox, cold etc

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Priyash Raj 3 years, 8 months ago

Corona, chicken pox

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Mohit Tanwar 3 years, 8 months ago

Covid -19 , cold

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Pragati Yadav 3 years, 8 months ago

Asthama , covid-19

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What is meant by a substance.

Posted by Swapnil Singh 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Ayushi Suryavanshi 3 years, 8 months ago

Any substance is said to be pure if and only if it is made up a single type of particles means all the particles of that substance should be of same chemical nature. For example water,sugar,salt, sodium,tin, etc.

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Rishika Dhindwal 3 years, 8 months ago

A substance is a pure single form of matter . It cannot separated into other kinds of matter by any physical process.

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Where are peroxisomes found??

Posted by Palak Goyal 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Priyal Gupta 3 years, 8 months ago

Peroxisomes are found in the cytoplasm of a eukaryotic cell

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If object in height that the potential energy. If the object no height and touch to earth surface then which energy on object?

Posted by Arpit Srivastav 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Palak Goyal 3 years, 8 months ago

Kinetic energy

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Your younger brother observes some mosquitoes sucking juices of cut fruit pieces, though it is common knowledge that mosquitoes suck blood of humans. How will you explain this behavior to him?

Posted by Varsha Gemnani 3 years, 8 months ago

CBSE > Class 09 > Science

0 answers

ANSWER

State the name and type of Force which is responsible for the formation of tides in the sea

Posted by Nisha Murali 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Ankush Ranjan 3 years, 8 months ago

Gravitational force

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Rishika Dhindwal 3 years, 8 months ago

Gravity

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What is an ideal bday wish for some

Posted by Sachi Khushalani 3 years, 5 months ago

CBSE > Class 09 > Science

1 answers

Sia ? 3 years, 5 months ago

“Wishing you a day filled with happiness and a year filled with joy. Happy birthday!” “Sending you smiles for every moment of your special day…Have a wonderful time and a very happy birthday!” “Hope your special day brings you all that your heart desires!

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According to Newton's third laws every action has equal and opposite reaction then why are able to carry the things like glass,bag, etc .??

Posted by Manish Kumar 3 years, 8 months ago

CBSE > Class 09 > Science

0 answers

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Give Note on Monera kingdom

Posted by Aditi Sinha 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Kajal Yadav 3 years, 8 months ago

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Explain bohr,s model of atom

Posted by Prachi Verma 3 years, 8 months ago

CBSE > Class 09 > Science

1 answers

Akshat Holland Minettee 3 years, 8 months ago

According to Bhor's Model of an Atom - 1) Only some special orbits called discrete orbits are allowed in an atom. 2) While revolving around the discrete orbits electrons do not radiate energy. 3) The shells or orbits in an atom are known as energy levels and are named as n= K, L, M, N and so on or 1,2,3,4...

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Atom and molecules notes

Posted by Bhupesh Yadav 3 years, 8 months ago

CBSE > Class 09 > Science

2 answers

Kripa Daga 3 years, 8 months ago

•Go in science column •Select chapter atoms and moleclues •select cbse revision notes •click on the row •scroll down and you have your notes •thanks

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Kripa Daga 3 years, 8 months ago

Laws of Chemical Combination Limitation of “Law of definite proportion” This law does not hold good when the compound is obtained by using different isotopes of the combining elements. 2. John Daltons Atomic Theory Using his theory, Dalton rationalized the various laws of chemical combination which were in existence at that time. However, he assumed that the simplest compound of two elements must be binary. 3. Atoms, Molecules, Ions & Chemical Formula Atom An atom is the smallest particle of an element which can take part in a chemical reaction. It may or may not exist freely. Each atom of an element shows all the properties of the element. Molecule The smallest particle of matter (element or compound) which can exist in a free state. The properties of a substance are the properties of its molecules. MOLECULES OF ELEMENT : The molecules of an element are constituted by the same type of atoms. MOLECULES OF COMPOUND: Atoms of different elements join together in definite proportions to form molecules of compounds. (hetero atomic molecules) ATOMICITY: The number of atoms contained in a molecule of a substance (element or compound) is called its atomic Element Formula Atomicity Ozone O3 3 Phosphorus P4 4 Sulphur S8 8 Oxygen O2 2 Based upon atomicity molecules can be classified as follows. Monoatomic molecules: Noble gases helium, neon and argon exist as He Ne and Ar respectively. Diatomic molecules: Triatomic molecules: SYMBOLS The abbreviation used to represent an element is generally the first letter in capital of the English name of element. Oxygen O Nitrogen N When the names of two or more elements begin with the same initial letter, the initial letter followed by the letter appearing later in the name is used to symbolize the element Barium Ba Bismuth Bi Symbols of some elements are derived from their Latin names ELEMENT LATIN NAME SYMBOL Sodium Natrium Na Copper Cuprum Cu Potassium Kalium K Iron Ferrum Fe Mercury Hydragyrum Hg Tungsten Wolfram W Polyatomic Ion : A group of atoms carrying a charge is as polyatomic ion. Eg. Valency : The number of electrons which an atom can lose , gain or share to form a bond. OR It is the combining capacity of an atom of the element. Chemical Formula : A chemical formula is a short method of representing chemical elements and compounds. Writing a Chemical Formula -CRISS-CROSS rule RULES > All subscripts must be reduced to lowest term (except for molecular or Examples CATION ANION FORMULA NAME Aluminium sulphate Ca Calcium bicarbonate Ammonium chloride Sodium carbonate Magnesium hydroxide Sodium phosphate 4. Mole Concept The mole (mol) is the amount of a substance that contains as many elementary entities as there are atoms in exactly 12.00 grams of The Avogadro constant is named after the early nineteenth century Italian scientist Amedeo Avogadro. GRAM MOLECULAR MASS Gram molecular mass is the mass in grams of one mole of a molecular substance. Ex: The molecular mass of is 28, so the gram molecular mass of is 28 g. ATOMIC MASS UNIT An atomic mass unit or amu is one twelfth of the mass of an unbound atom of carbon-12. It is a unit of mass used to express atomic masses and molecular masses. Also Known As: Unified Atomic Mass Unit (u). MOLECULAR MASS : A number equal to the sum of the atomic masses of the atoms in a molecule. The molecular mass gives the mass of a molecule relative to that of the 12 C atom, which is taken to have a mass of 12. Examples: The molecular mass of is approximately 30 or . Therefore the molecule is about 2.5 times as heavy as the 12C atom or about the same mass as the NO atom with a molecular mass of 30 or (14 +16). 5. Molar Mass & Avogadro Constant

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State and prove the law of conservation of energy

Posted by Divyanshi Mahajan 3 years, 8 months ago

CBSE > Class 09 > Science