# List of Posts written during May 2021

This is a list of of posts written during the month May 2021
(Rev. 14-Sep-2023)

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### List of Posts

This is the complete list of categories of posts written during May 2021. They have been ordered by the publish date, with the most recent first.

1. Published: 03-May-2021
Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation: N2 (g) + H2 (g) → 2NH3 (g)(i) Calculate the mass of ammonia produced if 2.00 × 103 g dinitrogen reacts with 1.00 ×103 g of dihydrogen. (ii) Will any of the two reactants remain unreacted? (iii) If yes, which one and what would be its mass?

2. Published: 03-May-2021
How are 0.50 mol Na2CO3 and 0.50 M Na2CO3 different?

3. Published: 03-May-2021
If 10 volumes of dihydrogen gas reacts with five volumes of dioxygen gas, how many volumes of water vapour would be produced?

4. Published: 04-May-2021
Which one of the following will have the largest number of atoms? (i) 1 g Au (s) (ii) 1 g Na (s) (iii) 1 g Li (s) (iv) 1 g of Cl2(g)

5. Published: 04-May-2021
Calculate the molarity of a solution of ethanol in water, in which the mole fraction of ethanol is 0.040 (assume the density of water to be one).

6. Published: 05-May-2021
What will be the mass of one 12C atom in g?

7. Published: 05-May-2021
Use the data given in the following table to calculate the molar mass of naturally occuring argon isotopes: Isotope Isotopic molar mass Abundance 36Ar 35.96755 g mol-1 0.337% 38Ar 37.96272 g mol-1 0.063% 40Ar 39.9624 g mol-1 99.600%

8. Published: 05-May-2021
Calculate the number of atoms in each of the following (i) 52 moles of Ar (ii) 52 u of He (iii) 52 g of He.

9. Published: 07-May-2021
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 (i) empirical formula, (ii) molar mass of the gas, and (iii) molecular formula.

10. Published: 07-May-2021
Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the reaction, CaCO3 (s) + 2 HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O(l) What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?

11. Published: 07-May-2021
Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2) with aqueous hydrochloric acid according to the reaction 4 HCl (aq) + MnO2 (s) → 2H2O (l) + MnCl2 (aq) + Cl2 (g) How many grams of HCl react with 5.0 g of manganese dioxide?

12. Published: 08-May-2021
(i) Calculate the number of electrons which will together weigh one gram. (ii) Calculate the mass and charge of one mole of electrons.

13. Published: 09-May-2021
(i) Calculate the total number of electrons present in one mole of methane. (ii) Find (a) the total number and (b) the total mass of neutrons in 7 mg of 14C. (Assume that mass of a neutron = 1.675 × 10-27 kg). (iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH3 at STP. Will the answer change if the temperature and pressure are changed ?

14. Published: 09-May-2021
Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wavenumber (ν) of the yellow light.

15. Published: 10-May-2021
What is the number of photons of light with a wavelength of 4000 pm that provide 1J of energy?

16. Published: 10-May-2021
A photon of wavelength 4 × 10-7 m strikes on metal surface, the work function of the metal being 2.13 eV. Calculate (i) the energy of the photon (eV), (ii) the kinetic energy of the emission, and (iii) the velocity of the photoelectron (1 eV= 1.6020 × 10-19 J).

17. Published: 10-May-2021
Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the sodium atom. Calculate the ionisation energy of sodium in kJ mol-1.

18. Published: 11-May-2021
A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.

19. Published: 12-May-2021
Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency (ν0 ) and work function (W0 ) of the metal.

20. Published: 12-May-2021
What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

21. Published: 13-May-2021
How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom ( energy required to remove the electron from n =1 orbit)

22. Published: 13-May-2021
What is the maximum number of emission lines when the excited electron of a H atom in n = 6 drops to the ground state?

23. Published: 14-May-2021
(i) The energy associated with the first orbit in the hydrogen atom is -2.18 × 10-18 J atom-1. What is the energy associated with the fifth orbit? (ii) Calculate the radius of Bohr's fifth orbit for hydrogen atom.

24. Published: 14-May-2021
Calculate the wavenumber for the longest wavelength transition in the Balmer series of atomic hydrogen.

25. Published: 18-May-2021
Which of the following are isoelectronic species i.e., those having the same number of electrons? Na+, K+, Mg2+, Ca2+, S2-, Ar.

26. Published: 19-May-2021
(i) Write the electronic configurations of the following ions: (a) H- (b) Na+ (c) O2- (d) F- (ii) What are the atomic numbers of elements whose outermost electrons are represented by (a) 3s1 (b) 2p3 and (c) 3p5 ? (iii) Which atoms are indicated by the following configurations ? (a) [He] 2s1 (b) [Ne] 3s2 3p3 (c) [Ar] 4s2 3d1.

27. Published: 20-May-2021
What is the lowest value of n that allows g orbitals to exist?

28. Published: 21-May-2021
An electron is in one of the 3d orbitals. Give the possible values of n, l and ml for this electron.

29. Published: 21-May-2021
How many electrons in an atom may have the following quantum numbers? (a) n = 4, ms = - ½ (b) n = 3, l = 0

30. Published: 21-May-2021
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.

31. Published: 21-May-2021
What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of He+ spectrum ?

32. Published: 25-May-2021
Calculate the energy required for the process He+ (g) → He2+ (g) + e- The ionization energy for the H atom in the ground state is 2.18 × 10-18 J atom-1

33. Published: 25-May-2021
An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.

34. Published: 26-May-2021
An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than the electrons, find the symbol of the ion.

35. Published: 26-May-2021
Following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) threshold wavelength and, (b) Planck's constant. λ (nm) 500 450 400 v × 10-5 (cm s-1) 2.55 4.35 5.35

36. Published: 26-May-2021
Calculate the wavelength for the emission transition if it starts from the orbit having radius 1.3225 nm and ends at 211.6 pm. Name the series to which this transition belongs and the region of the spectrum.

37. Published: 30-May-2021
The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electron in 4p orbital. Which of these electron experiences the lowest effective nuclear charge ?