If elements with principal quantum number n> 4 were not allowed in nature, the number of possible elements would be:
Alkanes are ____________.
Consider the following statements :
(1) An alloy is a mixture of two or more metals.
(2) An alloy is a mixture of a metal or metals with a non-metal.
Which of the statements given above is/are correct ?
Alkali metals belong to which group in periodic table?
The nuclear particles which are assumed to hold the nucleons together are ?
Iodine can be separated from a mixture of Iodine and Potassium Chloride by ?
What is the hardest form of carbon ?
Following statements are made in connection with carbon dioxide (CO2)
(1) CO2 is a poisonous gas.
(2) CO2 is an acidic oxide.
(3) CO2 turns limewater milky.
Which of the statements given above is/are correct?
Equimolar solutions in the same solvent have
Consider the following statements and select the correct code.
Assertion (A): The main constituent of the
liquefied petroleum gas is methane.
Reason (R): Methane can be used directly for burning in homes and factories where it can be supplied through pipelines.
The pH of water at 25°C is 7. When it is heated to 100°C, the pH of water:
Chemical used in photography is:
Amount of oxalic acid present in a solution can be determined by its titration with KMnO4 solution in the presence of H2SO4. The titration gives unsatisfactory result when carried out in the presence of HCl, because HCl:
Consider the following statements regarding diamond:
(1) It is an allotrope of silicon.
(2) It is a bad conductor of heat and electricity.
(3) It is the hardest substance.
(4) It burns to produce carbon dioxide.
Which of the statements given above are correct?
Beta rays emitted by a radioactive material are :
The number of electrons presents in H+ is:
Which of the following pairs are correctly matched?
(1) Isotopes : Atoms with same atomic number but different atomic mass.
(2) Isobars : Atoms with same number of neutrons but different atomic number.
(3) Isotones : Atoms with same mass number but different atomic number.
Select the correct answer using the codes given below :
Which of the following is the most active chemically?
What are the number of moles of CO2 which contains 16 g of oxygen?
Which of the following is an anti-knocking compound, that has been phased out in many countries so far?
Consider the following: Crude oil is a direct source of
(1) Asphalt (2) Paraffin wax
(3) Fatty acids (4) Gas oil
Which of the above are correct?
What is the most common isotope of hydrogen?
If α is the degree of dissociation of Na2SO4, the vant Hoff’s factor (i) used for calculating the molecular mass is:
The metallurgical process in which a metal is obtained in a fused state is called:
What is used to avoid melting of ice ?
The ore which is found in abundance in India is:
Chlorophyll molecules act as both donors and acceptors in fluorescence resonance energy transfer. The fluorescence lifetime of chlorophyll molecules in a dilute solution of an organic solvent wa found to be 1.2 ns. When chlorophyll molecules were instead embedded in a biopolymer, the fluorescence lifetime was measured to be 820 ps. Given that R0 = 5.6 nm for chlorophyll molecules, estimate the separation between the donor-acceptor pairs in the polymer.
Which is not a type of elements ?
Which of the following gases is the most toxic?
Which of the following copper alloys is used for the manufacture of springs and suspension filaments in electrical instruments?