List of top Chemistry Questions

Predict the formula of the stable binary compounds that would be formed by the combination of the following pairs of elements.
  1. Lithium and oxygen 
  2. Magnesium and nitrogen 
  3. Aluminium and iodine 
  4. Silicon and oxygen
  5. Phosphorus and fluorine 
  6. Element 71 and fluorine
Assign the position of the element having outer electronic configuration
  1. \(ns^ 2 np^ 4\) for \(n\) = \(3\) 
  2. \((n - 1)d^ 2 \;ns^ 2\) for \(n\) =\( 4\), and 
  3. \((n - 2) f ^7 (n - 1)d ^1 ns^ 2\) for \(n\) = \(6\), in the periodic table.
The increasing order of reactivity among group 1 elements is \(Li\) \(<Na\) \(<K\) \(<Rb\) \(<Cs\) 
whereas that among group 17 elements is \(F>Cl>Br>I\) Explain.
Use the periodic table to answer the following questions.
  1. Identify an element with five electrons in the outer subshell.
  2. Identify an element that would tend to lose two electrons. 
  3. Identify an element that would tend to gain two electrons.
  4. Identify the group having metal, non-metal, liquid as well as gas at the room temperature.
The first\((\triangle_ iH_1)\) and the second \((\triangle_iH)\) ionization enthalpies (in \(kJ\; mol ^{-1}\) ) and the \((\triangle_{eg}H)\) electron gain enthalpy (in \(kJ \;mol^{ -1}\) ) of a few elements are given below: 
Elements                       \(\triangle_iH\)                \(\triangle_iH\)                \(\triangle_{eg}H\) 
   I                                    520                   7300                    -60 
  II                                    419                   3051                    -48 
  III                                  1681                  3374                    -328  
  IV                                  1008                 1846                    -295 
  V                                   2372                  5251                   +48 
  VI                                  738                    1451                    -40
Which of the above elements is likely to be : 
  1. the least reactive element.
  2. the most reactive metal.
  3. the most reactive non-metal.
Neon gas is generally used in the sign boards. If it emits strongly at 616 nm, calculate 
(a) the frequency of emission
(b) distance traveled by this radiation in 30 s 
(c) the energy of quantum and 
(d) number of quanta present if it produces 2 J of energy.
Nitrogen laser produces radiation at a wavelength of 337.1 nm. If the number of photons emitted is 5.6 × 1024, calculate the power of this laser.
Arrange the following types of radiations in increasing order of frequency: 
(a) radiation from the microwave oven 
(b) amber light from a traffic signal 
(c) radiation from FM radio 
(d) cosmic rays from outer space and (e) X-rays.
An ion with mass number 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. Assign the symbol to this ion.
An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.
Symbols \(_{79}^{35}\textrm{Br}\) and \(_{79}^{}\textrm{Br}\) can be written, whereas symbols \(_{35}^{79}\textrm{Br}\) and \(_{35}^{}\textrm{Br}\) are not acceptable. Answer briefly.
In Rutherford’s experiment, generally the thin foil of heavy atoms, like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like aluminium etc. is used, what difference would be observed from the above results ?
If the diameter of a carbon atom is 0.15 nm, calculate the number of carbon atoms which can be placed side by side in a straight line across length of scale of length 20 cm long.
Write the general outer electronic configuration of \(s-, p-, d-\) and \(f-\) block elements.

Find the energy of each of the photons which (i) corresponds to light of frequency 3×1015 Hz. (ii) have a wavelength of 0.50 Å

In Milikan’s experiment, a static electric charge on the oil drops was obtained by shining X-rays. If the static electric charge on the oil drop is –1.282 × 1018C, calculate the number of electrons present on it.
What are the major differences between metals and non-metals?
The diameter of zinc atom is 2.6 Å. Calculate (a) radius of zinc atom in pm and (b) number of atoms present in a length of 1.6 cm if the zinc atoms are arranged side by side lengthwise.
2 ×108 atoms of carbon are arranged side by side. Calculate the radius of the carbon atom if the length of this arrangement is 2.4 cm.
Calculate the energy required for the process He+ (g)\(\rightarrow\)He2+ (g) + e– The ionization energy for the H atom in the ground state is 2.18 × 10–18 J atom–1
What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of He+ spectrum?
Show that the circumference of the Bohr orbit for the hydrogen atom is an integral multiple of the de Broglie wavelength associated with the electron revolving around the orbit.
A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate:
  1. empirical formula, 
  2. molar mass of the gas, and 
  3. molecular formula
Explain, giving reasons, which of the following sets of quantum numbers are not possible.
(a) n = 0, l = 0, ml = 0, ms = +\(\frac{1}{2}\) (b) n = 1, l = 0, ml = 0, ms = –\(\frac{1}{2}\) (c) n = 1, l = 1, ml = 0, ms = + \(\frac{1}{2}\) (d) n = 2, l = 1, ml = 0, ms = – \(\frac{1}{2}\) (e) n = 3, l = 3, ml = –3, ms = + \(\frac{1}{2}\) (f) n = 3, l = 1, ml = 0, ms = + \(\frac{1}{2}\)
Give the number of electrons in the species H+2 , H2 and O+2.