Ask questions which are clear, concise and easy to understand.

What is the difference between molar mass and molecular mass??

Posted by utkarsh chamoli (Feb 26, 2017 4:50 p.m.) (Question ID: 2694)

• Molar Mass and molecular Mass are same differnece is in there units only like molar mass is in gram/mole whereas molecular mass is in atomic mass unit {amu}

Answered by Joe Singhal (Feb 26, 2017 5:17 p.m.)
Thanks (0)

Describe conservation of energy

Posted by Ayush Kumar (Feb 26, 2017 2:10 p.m.) (Question ID: 2684)

• According to this law, the total energy of a system remains conserved. Energy can neither be created norbe destroyed.

Answered by Shweta Gulati (Feb 26, 2017 2:50 p.m.)
Thanks (0)

What are drawbacks of Rutherford's theory?

Posted by Gourav Chaudhary (Feb 26, 2017 12:41 p.m.) (Question ID: 2677)

• The main draw back of ratherford's model is that it doesn't explain the stability of atom

Answered by Sachin Sharma (Feb 26, 2017 1:37 p.m.)
Thanks (0)
• IT says that the electron revolve around the nucleus, but accordind to Maxwell's electromagnetic theory if a charged particle continuosly revolve around the nucleus, it will loose energy and eventually spiral into the nucleus and nucleus will collapse.But we know that nucleus is stable.

Answered by Devanshu Agarwal (Feb 26, 2017 12:47 p.m.)
Thanks (0)

What is echo ranging

Posted by Akshay Garg Garg (Feb 25, 2017 9:58 p.m.) (Question ID: 2667)

• 17.3 meters

Answered by Sachin Sharma (Feb 26, 2017 1:44 p.m.)
Thanks (0)
• Ans.Echo ranging is the process of detecting underwater objects using sound signals. The minimum distance between source and the reflecting body should be 17 meters for the formation of an echo. This technique is used to measure depth of sea with the help of Sonar.

Answered by Naveen Sharma (Feb 25, 2017 11:23 p.m.)
Thanks (0)

Determine the no. of H atom in sucrose(C12H22O11)

Posted by Sahil Sartaj (Feb 25, 2017 7:52 p.m.) (Question ID: 2659)

• The no. of atoms is total h in formula unit i.e. 22

Answered by Devanshu Agarwal (Feb 25, 2017 11:28 p.m.)
Thanks (0)

Distinguish between mole and molecule (b)calculate number of molecules in 0.1mole of H2O.also calculate number of Hatoms in it

Posted by Anuja Anil (Feb 25, 2017 6 p.m.) (Question ID: 2653)

• An atom is the basic unit of matter- a combination of protons, electrons, and neutrons. A molecule is several atoms bonded together. For example, hydrogen (H) and Oxygen (O) are atoms, but H20 (two hydrogen and one oxygen) is a molecule. A mole is simply a number.
It is 6.02214×10^23. A mole of hydrogen atoms means that there are 6.02214×10^23 hydrogen atoms. Molar Mass is the mass of 6.02214×10^23 of something. For example, 6.02214×10^23 or one mole of oxygen weighs 16 grams. 2 moles of oxygen would weigh 32 grams.

1 mole of H2O contains 6.022 * 10^23 molecules of H2O

Therefore 0.1 mole contains:- 0.1 * 6.022*10^23 = 6.022 * 10^22 molecules of H2O

Answered by Devanshu Agarwal (Feb 25, 2017 11:51 p.m.)
Thanks (1)

Calculate the relative molecular mass of HNO3

Posted by India K (Feb 25, 2017 4:44 p.m.) (Question ID: 2642)

• Relative Molecular mass = (1*1) + ( 1*14)+(16*3) = 1+14+48 = 63

Answered by Devanshu Agarwal (Feb 25, 2017 11:33 p.m.)
Thanks (0)

Calculate the formula unit mass of Na2S2O3 and cuSO4 5h2o

Posted by India K (Feb 25, 2017 4:42 p.m.) (Question ID: 2641)

• Ans. $$Na_2 S_2O_3$$

Atomic mass of Na = 23u
Atomic mass of S = 32u
Atomic mass of O = 16u

$$Formula \space Unit \space Mass\space of \space Na_2S_2O_3 = 2 \times 23 + 2\times 32 + 3\times 16$$

=> 46+64+48 = 158 u

$$CuSO_4.5(H_2O)$$

Atomic mass of Cu = 63 u
Atomic mass of S = 32u
Atomic mass of O =16 u
Atomic mass of H =8 u

$$Formula \space Unit \space Mass\space of \space CuSO_4.5(H_2O) =63.5 + 32 + 4\times 16 + 5[(2\times 1) +16]$$

=> 63.5+32+64 + 90 = 249.5 u

Answered by Naveen Sharma (Feb 25, 2017 5:19 p.m.)
Thanks (1)

1N/m2 is equal to

Posted by Premlata Awasare (Feb 24, 2017 9:45 a.m.) (Question ID: 2530)

• 1 pascal

Answered by Supriya Kumari (Feb 24, 2017 11:48 a.m.)
Thanks (0)
• Ans. 1Pascel

Answered by Naveen Sharma (Feb 24, 2017 10:33 a.m.)
Thanks (0)

Is the buoyant force works only in liquid?

Posted by Manisha Shukla (Feb 23, 2017 7:17 a.m.) (Question ID: 2485)

• Archimedes' principle states that "Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object."

Therefore, it is clear that the buoyant force works only in liquid.

Answered by Rashmi Bajpayee (Feb 23, 2017 10:21 a.m.)
Thanks (0)

Why Carbon-12 (C-12) atom is used as standard unit ?

Posted by Rudransh NATH (Feb 22, 2017 9:50 p.m.) (Question ID: 2477)

• The fact that the elements all seem to weigh multiples of the mass of hydrogen was noticed early in the history of chemical atoms, as soon as chemists started to determine atomic weight. They thought that all matter was made of hydrogen. But the element hydrogen was never used as an atomic mass standard, because it doesn't form compounds with enough other elements. The atom that does form compounds with every element known at that time, and almost all elements known now, is oxygen; and so for at least a century chemists assigned natural oxygen a mass of exactly 16 as a way of determining atomic weights by chemical methods.

Around the turn of the 20th Century, the physicists began measuring atomic weights of individual atoms, using mass spectrometry; they, too, used the oxygen standard, but they assigned the isotope O-16 a mass of exactly 16.

These standards are incompatible, because natural oxygen is a mixture of O-16, O-17 and O-18. For chemists, setting oxygen's average atomic mass to 16 was convenient, because chemists were determining the masses using bulk chemistry, but for mass spectrometrists it certainly was not a convenient standard!

The dilemma was solved by assigning C-12 a mass of exactly 12.

Answered by Shweta Gulati (Feb 23, 2017 11:29 p.m.)
Thanks (0)
• Because mass of one mole C12  carbon is 12g

Answered by Supriya Kumari (Feb 22, 2017 11:42 p.m.)
Thanks (0)

A bat emits ultrasond wave of 30000Hz if the speed of sound is 350 m/s and the bat hears its echo after 0.6 second find how far the bat and.obstacle and the.wave length

Posted by Kartik Rahi (Feb 22, 2017 8:28 p.m.) (Question ID: 2470)

• Speed of sound = 350 m/s

Echo time = 0.6 s

i.e. time = 0.6/2 =0.3s

Distance of the bat and obstacle = speed X time

= 350 X 0.3 = 105 m

$${\lambda }$$= velocity / frequency

= 350/30000 = 11.7 X 10-3 m

Answered by Shweta Gulati (Feb 23, 2017 11:35 p.m.)
Thanks (0)
• frequency of ultrasound= 30000Hz

Answered by Rudransh NATH (Feb 22, 2017 9:54 p.m.)
Thanks (0)

A mole is quite often called chemist's dozen.Explain.

Posted by Debaditya Ghosh (Feb 22, 2017 11:06 a.m.) (Question ID: 2437)

• Ans. A dozen is a common counting unit. A counting unit is a convenient number that makes it easier to count objects. We ofen count doughnuts and eggs by dozens. Similarly, we count shoes and gloves in pairs. Chemists, however, do not work with macroscopic (visible) objects like shoes and doughnuts. Instead, chemists are interested in microscopic entities: atoms and molecules. Since these entities are so small, chemists established their own practical counting unit called the mole. So we can say that A Mole is a Chemist Dozen.

Answered by Naveen Sharma (Feb 22, 2017 12:07 p.m.)
Thanks (0)

A bag filled with air has volume of 500 cubic cm. Calculate force required to immerse it completely in water.

Posted by Aryan Malewar (Feb 22, 2017 7:15 a.m.) (Question ID: 2426)

• Ans. We know

$$Density \space of \space water \space (\rho )= 1 g/cm³ = 10^3 kg/m^3$$

$$Volume \space of \space Air\space in\space Bag \space (V) = 500cm^3 = 5\times 10^{-4}m^3$$

$$Gravity (g) = 10 m/s$$

$$Minimum \space Force \space Required = Buoyant \space Force = \rho\times V\times g$$

=> $$10^3 \times 5 \times 10^{-3}\times 10 = 5N$$

Answered by Naveen Sharma (Feb 22, 2017 3:36 p.m.)
Thanks (1)

What is freefall

Posted by spandan Mukhopadhyay (Feb 22, 2017 12:07 a.m.) (Question ID: 2425)

• It is the condition of unrestrained motion in a gravitational field. For e.g.: Parachute Jump before the parachute opens.

Answered by Manish Gandhi (Feb 22, 2017 12:30 p.m.)
Thanks (0)

Why  can't  the number of protons be more than number of neutrons in an atom?

Posted by Pranzal Kumar Sinha (Feb 21, 2017 8:35 p.m.) (Question ID: 2410)

• The reason is that protons, being charged particles, repel each other. As you get to heavier elements, with each new proton you add, there is a larger repulsive force. The nuclear force is attractive and stronger than the electrostatic force, but it has a finite range. So you need to add extra neutrons, which do not repel each other, to add extra attractive force.

Answered by Shweta Gulati (Feb 21, 2017 9:12 p.m.)
Thanks (2)

a man fires a bullet towards cliff and hears echo after 4 sec he moves towards the clife nabout 150m and agains fire now he hears echo after3.6s what is the distance from his first position[ASSUME VELOCITY OF SOUND IS NOT KNOWN TO YOU]

Posted by Yuvraj Singh (Feb 21, 2017 5:31 p.m.) (Question ID: 2400)

• Ans. Let the Distance  b/w cliff and man = d m

Then total distance cover by sound = 2d m

Velocity of Sound = v

Then

$$v = {2d \over 4} = {d\over 2}\space\space\space\space\space\space\space\space\space\space ......[1]$$

As He move 150m  towards The cliff,

Now distance b/w man and cliff = d-150 m

Total distance covered by Sound = 2(d-150) m

So

$$v = {2(d-150)\over 3.6} = {2(d-150)\times 10\over 36} = {5(d-150)\over 9} \space \space \space \space \space ......[2]$$

As velocity of sound is same, then

from (1) and (2)

=> $${d\over 2}= {5(d-150)\over 9}$$

=> $$9d = 10d - 1500$$

=> $$10d- 9d = 1500 => d = 1500$$

Distance b/w man and cliff = 1500 m

Answered by Naveen Sharma (Feb 21, 2017 5:49 p.m.)
Thanks (2)

State some of the uses of Gymnosperms with its source.

Posted by JD Shukla (Feb 20, 2017 9:06 p.m.) (Question ID: 2372)

• Ans. Some plants seeds are edible, rich in starch and stems and leaves are used for making wine while leaves, pollen, bark and oil of some species are an effective ingredient in medicines. The ornamental trees are utilized in landscaping and parks. In industry, pulp and wood from the plants produce everything from pencils to turpentine. Conifers, such as pine and cedar, provide lumber and some species are used for nail polish, soap and perfume.

Answered by Naveen Sharma (Feb 20, 2017 9:40 p.m.)
Thanks (1)

Name the products obtained from some of the pteridophyta also tell the source.

Posted by JD Shukla (Feb 20, 2017 9:05 p.m.) (Question ID: 2371)

• Some examples are marsilea, ferns and horse-tails.
• Pteridophytes are used for medicinal purposes and as soil-binders. They are also frequently grown as ornamentals.
Answered by Shweta Gulati (Feb 21, 2017 7:32 p.m.)
Thanks (1)

How can we use algae ? Please explain in detail.

Posted by JD Shukla (Feb 20, 2017 9:03 p.m.) (Question ID: 2370)

• Humans use algae as food, for production of useful compounds, as biofilters to remove nutrients and other pollutants from wastewaters, to assess water quality, as indicators of environmental change, in space technology, and as laboratory research systems. Algae is commercially cultivated for Pharmaceuticals, Nutraceuticals, Cosmetics and Aquaculture purpose.

Answered by Shweta Gulati (Feb 21, 2017 7:35 p.m.)
Thanks (0)

find the number of electron ,proton,&neutron possessed by the alpha particles(4/2He+++)used in the gold leaf experiment.

Posted by Ankit Jhinjhonkar (Feb 20, 2017 9:25 a.m.) (Question ID: 2352)

• Ans.

Number of Electron = 0

Number of Proton = 2

Number of Neutron = 2

Answered by Naveen Sharma (Feb 20, 2017 12:14 p.m.)
Thanks (0)

Why all the isotopes are not placed in periodic table?

Posted by SUMANA ROY (Feb 19, 2017 10:17 p.m.) (Question ID: 2345)

• Since all the isotopes of an element have the same atomic  number,they can be put at one place in the same group of the periodic table. For example,both the isotopes of chlorine, Cl-35 and Cl-37 ,have the same atomic number of 17,so both of them can be put at one place in the same group of the periodic table.

Answered by Shweta Gulati (Feb 20, 2017 12:38 a.m.)
Thanks (1)

Weight of an empty glass is 1N. When it is completely filled with water the weight observed is 4N. If you throw the water and fill the empty glass partly with sand and its weight becomes 4N, if the rest of glass is now filled up with water, the weight becomes 6N, what is relative density of sand?

Posted by Harsh Jain (Feb 19, 2017 9:35 p.m.) (Question ID: 2344)

• Weight of empty glass = 1N

Weight of water alone = 4N-1N= 3N

Weight = mg

Mass of water = 3/9.8 = 0.306 kg

Density of water = 1000kg/m3

Volume of glass = 0.306/1000 = 3.06 X 10-4 m3

Weight of half glass sand = 4N-1N =3N

Weight of full glass sand = 3N+3N = 6N

Mass of full glass sand= 6N/9.8 = 0.612kg

Density of sand = Mass of sand/Volume of glass = 0.612/(3.06 X 10-4= 2000kg/m3

Relative density of sand = Density of sand/Density of water

= 2000/1000 =2

Answered by Shweta Gulati (Feb 20, 2017 12:52 a.m.)
Thanks (0)

The velocity of an object is suddenly doubled.if its kinetic energy earlier was 100 j what is the new kinetic  energy?

Posted by AARTI SHARMA (Feb 19, 2017 11:59 a.m.) (Question ID: 2326)

• Kinetic energy = 1/2 mv2

If velocity is doubled then KE increases  4 times.

So the answer would be 4*100= 400 joules

Answered by ayush das (Feb 19, 2017 12:13 p.m.)
Thanks (0)

A sound produced have 20 rarefaction and compressions in 0.2 sec . Distance between compression and rarefaction is 50cm find wavelength ,frequency,and time period of wave.

Posted by SHRI NIWAS JAT (Feb 19, 2017 10:02 a.m.) (Question ID: 2324)

• Since time perios is the time taken to complere one rarefaction and one compression:-

Now, time taken to complete 20 compressions and rarefactions:- 0.2 sec:-

time taken to complere one rarefaction and one compression = 0.2/20

= 0.01sec = time period

Since f=1/t

Therefore f= 1/0.01 = 100 hz

and labda = 2*50=100cm

Answered by Devanshu Agarwal (Feb 19, 2017 11:03 a.m.)
Thanks (1)

A sound wave has frequency of 2 kHz and wavelength 40 cm . Calculate time taken in 1.6 km

Posted by SHRI NIWAS JAT (Feb 19, 2017 9:59 a.m.) (Question ID: 2323)

• Since s=wavelength * frequency ( s= speed of sound)

Therefore :- s  = (40/100) * 2000

= 800 m/s

Therefore time taken = (1600)/800

= 2 sec

Answered by Devanshu Agarwal (Feb 19, 2017 10:43 a.m.)
Thanks (1)

What is formula of finding time period in  chapter sound

Posted by SHRI NIWAS JAT (Feb 19, 2017 9:57 a.m.) (Question ID: 2321)

• Since time period(T) is the time taken to complete one cycle

and frequency(f) is the no. of cycles completed in 1 sec:-

THerefore T = 1/f.

Answered by Devanshu Agarwal (Feb 19, 2017 10:48 a.m.)
Thanks (1)

What is natural resources

Posted by Arpan Mandal (Feb 18, 2017 10:27 p.m.) (Question ID: 2309)

• the substances obtained from natural sources like sun,  plant (renewable or non renewable) are called natural sources.

Answered by Supriya Kumari (Feb 18, 2017 11:49 p.m.)
Thanks (0)

Please give some exceptional organisms of each kingdom with its exceptional characteristics

Posted by JD Shukla (Feb 18, 2017 10:11 p.m.) (Question ID: 2306)

please some of the exceptional spieces for each kingdom with its exceptional characteristics.

Posted by JD Shukla (Feb 18, 2017 10:09 p.m.) (Question ID: 2305)

Posted by JD Shukla (Feb 20, 2017 8:50 p.m.)