Which process is responsible for producing photons in a diode laser?
A. Fermi level shift
B. Majority carrier injection
C. Carrier freeze out
D. Electron-hole recombination
Answer
Correct Answer: D. Electron-hole recombination
The Lanthanoids are part of which block of elements in the periodic table?
A. p-block
B. s-block
C. d-block
D. f-block
Answer
Correct Answer: D. f-block
Detailed About MCQs
Lanthanoids form part of the series of chemical elements comprising the 15 metallic chemical elements with atomic numbers 57 through 71, from lanthanum through the lutetium. They are a part of the f-block of elements in the periodic table.
Which of the following group of elements contain the noble gases?
A. s-block
B. p-block
C. d-block
D. f-block
Answer
Correct Answer: B. p-block
Detailed About MCQs
The p-Block Elements comprise those belonging to Group 13 to 18 and these together with the s-Block Elements are called the Representative Elements or Main Group Elements. The 18th group i.e. the last group of the p-block elements is the noble gas group.
Which method can be used to prevent rancidity?
A. Adding antioxidants to the food
B. Storing food at low temperature
C. Replace the air with nitrogen in the packing material
D. All of the above
Answer
Correct Answer: D. All of the above
Detailed About MCQs
When food containing fats and oils are exposed to the atmosphere, the oxidation of fat and oil occurs, this is called as Rancidity.
What is the S.I unit of activity?
A. becquerel
B. curie
C. candela
D. henry
Answer
Correct Answer: A. becquerel
Detailed About MCQs
The SI unit for activity is becquerel, named after the discoverer of radioactivity, Henry Becquerel. The c.g.s unit of activity is curie.
What is Rose metal?
A. It is an alloy of Nickel, Tin, and Zinc
B. It is an alloy of Bismuth, Copper, and Palladium
C. It is an alloy of Palladium, Tin, and Lead
D. It is an alloy of Bismuth, Tin, and Lead
Answer
Correct Answer: D. It is an alloy of Bismuth, Tin, and Lead
Detailed About MCQs
Rose metal is an alloy of Bismuth, Tin, and Lead. It’s a fusible alloy with a low melting point commonly used for soldering.
What is the hemihydrate of calcium sulfate commonly known as:
A. Gypsum
B. Plaster of Paris
C. Chloroform
D. Limestone
Answer
Correct Answer: B. Plaster of Paris
Detailed About MCQs
Plaster of Paris is the common name of calcium sulfate hemihydrate because half molecule of water is attached with calcium sulfate. The chemical formula of the plaster of Paris is CaSO4.1/2H2O.
What is the general trend for ionization enthalpies of alkali metals as we move down the group?
A. it increases
B. it decreases
C. it is the same for all
D. None of these
Answer
Correct Answer: B. it decreases
Detailed About MCQs
The ionization enthalpies of the alkali metals are considerably low and decrease down the group from Li to Cs.
What is the general trend for atomic radii of alkali metals as we move down the group?
A. it increases
B. it decreases
C. it remains constant
D. None of these
Answer
Correct Answer: A. it increases
Detailed About MCQs
The atomic and ionic radii of alkali metals increase on moving down the group i.e., they increase in size while going from Li to Cs.
Which chemical is also known as “Chinese snow”?
A. Silver iodide
B. Potassium nitrate
C. Ammonium chloride
D. Sodium phosphate
Answer
Correct Answer: B. Potassium nitrate
Detailed About MCQs
Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as saltpeter. It is also known as “Chinese snow”. Major uses of potassium nitrate are in fertilizers, rocket propellants, and fireworks.