One liter of pure water has a mass of one kilogram – the density of water is therefore 1 g/cm3 (1,000 gram/1,000 cubic centimeters) or 103 kg/m3
By saying that the density of water is 1000 kilograms per cubic meter we mean that the mass of 1 cubic meter volume of water is 1000 kilograms.
Ques.43. The elements with atomic number 2, 10, 18, 36 and 54 are all
Light metals
Halogen
Rare earth
Noble gases
Answer.4.Noble gases
Explanation:-
The elements with atomic numbers 2, 10, 18, 36, 54, and 86 are all chemically inert gases. The noble gases are in Group 18 in the periodic table. They are the most stable element due to their completely filled valence shell.
2 = He (Helium) 10 = Ne (Neon) 18 = Ar (Argon) 36 = Kr (Krypton) 54 = Xe (Xenon) 86 = Rn (Radon)
Ques.44. For complete combustion of 1 kg of carbon _______ oxygen is required
8 kg
8/3 kg
3/8 kg
1 kg
Answer.2. 8/3 kg
Explanation:-
For complete combustion, carbon combines with oxygen to carbon-di-oxide thus
C + O2 = CO
The molecular weight is
12 + 2(16) = 44 ———(1)
That is 12kg of carbon combine with 32 kg of oxygen to produce 44 kg of carbon dioxide. In 1 kg fuel, there is
Dividing eqn 1 by 12
1kg (C) + 8/3 kg(O2) = 11/3 kg of CO2
i.e if we had 1kg of carbon, it would take 8/3 kg of oxygen to burn it to 11/3 Kg of carbon dioxide
Ques.45. The atomic number of an element is determined by
The number of electrons in one atom
The number of neutrons in one atom
The valency of the elements
The number of protons in one atom
Answer.4. The number of protons in one atom
Explanation:-
The atomic number of an element is determined by the number of protons in the nucleus of an atom of the element. The mass number of an isotope is determined by the total number of neutrons and protons in the nucleus.
Ques.46. Girls ate sweet while fanning the files away. Due to this, she suffered from a disease diagnosed as
Cancer
Cholera
Diphtheria
Tuberculosis
Answer.2. Cholera
Explanation:-
Cholera is caused by infection with comma-shaped bacteria called Vibrio cholera. Typically the bacteria are ingested in food or water that has been contaminated with infected feces. However, cholera bacteria also live naturally in some warm coastal seawater and can contaminate local fish and shellfish. Human infection can then occur through eating raw contaminated seafood. Direct person-to-person transmission of cholera is extremely rare.
Ques.47. The burning of fossil fuels is the main cause of:
Nitrogen oxide pollution
Nitrous oxide pollution
Sulfur dioxide pollution
Nitric oxide pollution
Answer.3. Sulfur dioxide pollution
Explanation:-
One of the main sources of air pollution is burning fossil fuels like oil, gasoline, and coal. Burning fossil fuels releases pollutants into the air.
Many of the problems with fossil fuels are worse for coal than for oil or natural gas. Burning coal releases more carbon dioxide than either oil or natural gas.
Another problem with coal is that most coal contains sulfur. As it burns, the sulfur goes into the air as sulfur dioxide. Sulfur dioxide is the main cause of acid rain. Acid rain can be deadly to plants, animals, and whole ecosystems. Burning coal also puts a large number of small solid particulates into the air. These particles are dangerous to people, especially those who have asthma.
Ques.48. Gypsum is a
Mechanically formed sedimentary rock
Igneous Rock
Chemically precipitated sedimentary rock
Metamorphic rock
Answer.3. Chemically precipitated sedimentary rock
Explanation:-
Types of sedimentary rocks
ORGANIC SEDIMENTARY ROCKS
This group includes rocks that have a high content of organic material or have been formed by organic processes. Many limestones are organic, as they contain many shells or other fossil material. Coral-rich limestones may represent original reef environments cemented by lime mud. Coal, formed mainly of carbon derived from plants, is an organic rock of high economic value.
CHEMICAL SEDIMENTARY ROCKS
Inorganic chemical activity produces some sedimentary rocks, including colitic limestones, where calcium carbonate is precipitated around small nuclei in warm agitated seawater. Rock gypsum and rock salt are formed through chemical precipitation in evaporite basins when bodies of saline water dry up, and certain ironstones are formed chemically.
Ques.49. Chromosomes are concerned with
Respiration
Assimilation
Transmission of hereditary characteristics
Nutrition
Answer.3. Transmission of hereditary characteristics
Explanation:-
Heredity, the transmission of genetic characteristics from parent to offspring, is a significant determinant of growth and development.
Chromosomes:- Usually, DNA exists as threadlike structures floating in an unorganized manner within the nucleus of the cell. At certain stages of cell reproduction DNA becomes highly condensed and organized into structures called chromosomes.
There are normally 46 chromosomes in the nucleus of somatic cells During cell division chromosomes physically pair. Twenty-two chromosome pairs are called autosomes and are the same in everyone. The 23rd pair makes up the sex chromosomes. Normal females have two sex chromosomes and normal males have an X and a Y chromosome Mature sperm or egg cells have half the chromosomes (23) of somatic cells. During germ cell division, one chromosome from each chromosome pair is distributed randomly in daughter cells, resulting in the random combinations of maternal and paternal chromosomes. This process of random assortment is one of the primary mechanisms through which human variation occurs. When the ovum and sperm unite at conception, the total number of nuclear chromosomes it restored to 46.
Ques.50. Cod liver oil derived from fish is a rich source of
Vitamin C
Vitamin B12
Vitamin D
Vitamin B1
Answer.3. Vitamin D
Explanation:-
The term “fish oily usually refers to products derived from the fish body not the livers Fish oil does not mean cod liver Oils Unlike cod liver oil, fish body oils do not contain vitamins A and D.
Cod liver oil is a naturally rich source of vitamins A and D. Vitamin A has several important functions in the body; it is responsible for proper vision, immune system health and maintenance, and growth of skin and mucous membranes. Vitamin D helps regulate and control the metabolism of calcium and phosphorus by aiding in the absorption of these two minerals from the small intestine, and by directly affecting the rate at which these minerals form and maintain bone