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1. ### Trigonometry- addition and factor forumla

Homework Statement If tan(A+B) = 3 and tan(A-B) = 2, find tan2A and tan2B Homework Equations tan (A - B) = (tan A - tan B)/(1 + (tan A)(tan B) and similar sort of one for tan(A+B) The Attempt at a Solution i did some calculation and got tanA= (1-2tanB)/5tanB after which there...

Got it.
3. ### Bombing from an aeroplane

Then what about the theory part, I can only imagine those situations- to convert them into paper is somewhat difficult
4. ### Bombing from an aeroplane

Homework Statement A bomb is dropped from a plane flying horizontally with uniform speed. Show that the bomb will explode vertically below the plane. Is the statement true if the plane flies with uniform speed but not horizontally? Homework Equations Equations of projectile perhaps...
5. ### Chemistry Calculating the Concentration of N/5 HCl After Removal of 3.65g

Homework Statement On boiling 1litre of N/5 HCl, the volume of the aqueous solution decreases to 250ml. If 3.65g of HCl is removed from solution, then the concentration of resulting solution becomes? N/5 N/2.5 N/20 N/10 Homework Equations HCl=36.5g/ mol The Attempt at a Solution...
6. ### Biology Permutation and combination

Homework Statement A crew of an 8 oar boat has to be selected from 11 people, out of which 5 can oar only on one side, 4 can oar only on the other side and 2 can oar on either sides, find in how many ways can the selection be done? The Attempt at a Solution What I did here is assumed...
7. ### Permutation and combination

as per the answer given, you will need to consider both the cases!
8. ### Permutation and combination

Homework Statement how many 4 digit numbers are there which do not contain more than 2 different numbers? Homework Equations The Attempt at a Solution all can contain the same digit any 3 out of the 4 places can be occupied by the same digit and any 2 out of the 4 places can...
9. ### Permutation and combination

Homework Statement There are 15 players, out of which 4 players own one 4 seater car each, and the car will be driven by the owner himself. In how many ways can they be seated in the cars? Homework Equations (3n)!/(n!)3 The Attempt at a Solution i know that i have to substitute...
10. ### Indicate no of sigma and pi bonds

Homework Statement find total sigma and pi bonds in c6h6 Homework Equations Benzene structure The Attempt at a Solution if i consider benzene structure, then total will be 12σ and 3∏ but according to the random structure that i managed to draw, it showed, 11σ and 4∏, was i wrong...

12. ### Hybridization of carbon in carbonyl group

Homework Statement CH3CN [ in presence of aq. H2SO4 and 2H2O] → CH3COOH + NH3 The Attempt at a Solution There is a triple bond present between Carbon and nitrogen, hence the first will be sp hybridized, while there is double bond between carbon and oxygen in the second, hence it should...
13. ### Total Bonds in Ethyne - 3σ & 2π

Homework Statement In the hybradization of ethyne molecule, how many σ and ∏ bonds are being formed? The Attempt at a Solution Since, there is a triple bond between the carbon atoms, it should form 2 ∏ bonds and 1 σ bond. Relatively there will be 2 other σ bonds between Carbon-Hydrogen...

1 mole
15. ### Chemistry Moles in 1 mole nitride ion

That was my typing mistake!
16. ### Concentration of sulphate ion

3 moles, is this the answer?

Thanks!
18. ### Chemistry- Atomic Sturcture

yeah, got it! i was actually initially confused regarding that while typing, but now got it. But while referring to the solution of this sum, they had considered the third excited state when n= 3, which i don't think is true, do you agree? it should be n=4
19. ### Angular momentum for third electron of Lithium

So, what do you think, my answer is right?
20. ### Angular momentum for third electron of Lithium

Homework Statement For the third electron of Lithium atom moving in its permissible orbit, the values of angular momentum and the energy are? Homework Equations E= -2π2e4mZ2/n2h2 Third electron is in the second orbit The Attempt at a Solution The value for energy should be...
21. ### Concentration of the resulting solution in this question

Homework Statement On boiling 1litre N/5 HCl, the volume of the aqueous solution decreases to 250mL. If 3.65g of HCl is removed from the solution then the concentration of resulting solution becomes? Homework Equations No idea, from where should i start
22. ### Maximum unpaired electrons in an atom

Homework Statement If there are 13 electrons in M shell and one electron in N shell, the the number of unpaired electrons in such atom will be Homework Equations M- shell N- shell The Attempt at a Solution The configuration should be 3s2 3p6 3d5 4s1 hence the answer should be 6
23. ### Number of protons

Homework Statement The number of protons in nucleus of an element having maximum unpaired electrons in its 2P subshell are: Homework Equations Number of protons = no. of electrons in an neutral atom The Attempt at a Solution Maximum unpaired E.C. should 1s22s22p 3 Then, no. of...
24. ### Concentration of sulphate ion

Homework Statement The concentration of Al3+ ion in aqueous solution of Al2(SO4)3 is 0.28M, Then the concentration of SO42- ion in this solution will be? Homework Equations Al2(SO4)3 → 2Al3+ + 3SO42- The Attempt at a Solution What should i compare to start of with?
25. ### Chemistry Moles in 1 mole nitride ion

Homework Statement The number of moles of valence electrons in 1 mole nitride ions are? Homework Equations Nitride ion- N3- The Attempt at a Solution The number of electrons are 8. Therefore number of moles should also be 8?
26. ### Chemistry- Atomic Sturcture

Homework Statement The hydrogen electron de-excites from its 3rd excited state, which are the true and false statements for it. 1. It emits radiation giving lines in Lymann, Balmer, Paschen series 2. It emits radiation of only UV and Visible region and not Infrared region 3. It emits radiation...
27. ### Solving Straight Lines Homework: Find Intersection Point

Homework Statement Lines li: ix+(i+1)y+(i+2)=0; i=1,2 intersect at___ point? Homework Equations The equation is required at first! The Attempt at a Solution I am confused! How and where should I replace the values of i with 1 or 2? This is the first step but i am unable to do...
28. ### If each orbital can hold a maximum of 3 electrons

This question is just to develop the thinking skill of the student! It does not/ never is related to the original/factual happening around or perhaps inside the nucleus. From where should i start. I guess, the moment i get the completely filled configuration of noble gas, the number of...
29. ### Angle made by angular momentum

Homework Statement The angle made by angular momentum vector of an electron with Z- axis is given as ? Homework Equations angular momentum= √l(l+1) h/2∏ The Attempt at a Solution
30. ### Calculating size from energy

I will try to upload my solution, and perhaps from there, you can help me out
31. ### Calculating size from energy

So, I need to calculate the ratio of the energies of the two given? if yes then, I did this at first but the answer given, i.e. 14.82 times larger was not obtained
32. ### If each orbital can hold a maximum of 3 electrons

Homework Statement If each orbital can hold a maximum of 3 electrons, the number of elements in the 4th period of long form of periodic table will be? Homework Equations ? The Attempt at a Solution I am not able to decide from where should I begin?
33. ### Calculating size from energy

Homework Statement How many times larger is the spacing between the energy levels with n=3 and n=8 spacing between the energy levels with n=8 and n=9 for hydrogen atom? Homework Equations En=Rh[1/ni2- 1/nf2] The Attempt at a Solution From the above stated equation, i managed to...
34. ### Representation of quantum numbers +1/2 and -1/2

Homework Statement The quantum numbers +1/2 and -1/2 for the electron spin represents? Homework Equations a) rotation of electron in clockwise and anticlockwise directions respectively b) tow quantum mechanical spin states which have no classical analogue c) Magnetic moment of electron...
35. ### Kinetic energy of the emitted electrons

Homework Statement When the frequency of light incident on a metallic plate is doubled, the K.E. of the emitted photoelectrons will be? Homework Equations The answer should be either doubled or increased but more than double of the previous kinetic energy The Attempt at a Solution λ=...
36. ### Converting volts into energy

Homework Statement What possibility can be the ratio of the de Broglie wavelengths for electrons accelerated through 50 volts and 200 volts, initially having same wavelengths? Homework Equations I have literally no idea how to convert volts into energy, here i somewhat i think, Energy=...
37. ### Finding approx. minimum value for 'v'

Actually, I would like to quote this to everyone who has helped me including you, Dharavbhai, that my first answer to the question, the moment I saw was 4m/s but it was not given in the options and plus, somehow i forgot to write that in the calculations done list as well! the correct answer...
38. ### Finding approx. minimum value for 'v'

ok... so the answer is 4m/s, but that doesn't appears in the options given to me?

40. ### Finding approx. minimum value for 'v'

Ok... so the time I managed to calculate is 0.5s, what next? should i use the time in any of the equations of the motion, here the acceleration is 0.
41. ### Find minimum velocity of emitted electron

The answer what i got after considering 77eV as the kinetic energy, was not the original one, the answer should be 1.058m/s I mentioned in my previous comments all the possible values that I managed to find, kindly check them and let me know if i have made a mistake, even the concept and its...
42. ### Find minimum velocity of emitted electron

The energy of the electron, i got is 77eV, is it correct? But I am suppose to find the velocity of the electron?
43. ### Find minimum velocity of emitted electron

Homework Statement Photoelectric experiment show that about 5eV of energy are required to remove an electron from platinum, if light of 150nm wavelength is used, what is the velocity of the emitted electron? Homework Equations de broglie's equation, E=hv The Attempt at a Solution Tried by...
44. ### Finding approx. minimum value for 'v'

I have only the intial velocity of the truck and that of the paedestrian, no final velocity! How can I manage to calculate this without the final velocity? Assume it to be 0?
45. ### Finding approx. minimum value for 'v'

What do you want me exactly to do? As I had posted in the question itself, i had drewed the diagram, and perhaps imagine every incident that can take place in my mind, but any hints for getting the answer?
46. ### Finding approx. minimum value for 'v'

Homework Statement A 2m wide truck is moving with a uniform speed v=8m/s along a straight horizontal road a pedestrian starts to cross the road with a uniform speed u when the truck is 4m away from him minium value of v? Homework Equations The equations of motion in a straight line, and...
47. ### Finding valencies from a given element in 3 oxides

I used the molecular mass of O as 16 to derieve the molecular masses of each element, where I have confusion is that after finding the molecular masses of the oxides, how can I find the valencies, means, how is the molecular mass related with valency?
48. ### Calculating the percentage of silica

I had that stuff in my mind but couldn't manage to calculate further
49. ### Finding valencies from a given element in 3 oxides

Homework Statement The oxides of a certain element contain 27.28%, 42.86% and 52.94% oxygen. What is the ratio of valencies of the element in the 3 oxides? Homework Equations The Attempt at a Solution Following calculations were made: Molecular mass of the first oxide is 58.6...
50. ### Calculating the percentage of silica

Homework Statement A partially dried clay mineral contains 8% of water, the original sample contained 12% water and 45% silica. Then, the percentage of silica in the partially dried sample is nearly? Homework Equations Don't know if this is would help in the calculation, in the original...