chemistry for grade 7\\

The phosphorus present in an organic compound is oxidized to phosphoric acid by heating with fuming nitric acid. The phosphoric acid so obtained is precipitated as MgNH 4 PO 4 , which on ignition is converted into Mg 2 P 2 O 7 . From the mass of Mg 2 P 2 O 7 , the mass of phosp..

The heat changes are measured in calories (cal), kilo calories (kcal), joules (J) or kilojoules (kJ). These are related as: 1 cal = 4.184J 1 kcal = 4.184kJ The S.I. unit of heat is joule or kilojoule Work is measured in terms of ergs or joules. I Joule = 10 7 ergs. 1calorie = 4.184 x 10..

Mass number of 1 4 C is 14. So 14 g of 1 4 C contain 6.023 x 10 2 3 atoms of 1 4 C = 3.012 x 10 2 0 atoms Number of neutrons in 1 atom of 1 4 C = 14 - 6 = 8 Number of neutrons in 7 mg of 1 4 C = (8 x 3.012 x 10 2 0 ) = 24.1 x10 2 0 Mass of the neutron = mass of hydroge..

Cl = 35.5 1 mole of a substance = 22.4L 1 Mole of a substance = 1 GMM 1 GMM of Cl 2 = 71 g 71 g of Cl 2 = 22.4 L 7.1 g of Cl 2 = ? 7.1 g of Cl 2 will occupy a volume of 2.24 lite..

Fullerenes are recently discovered (1985) allotropes of carbon. They have been found to exist in the interstellar dust as well as in geological formations on earth. They are large cage like spherical molecules with formulae C 3 2 , C 5 0 , C 6 0 , C 7 0 , C 7 6 , C 8 4 ..

7. Classify each of the following equilibrium as homogeneous or heterogeneous: ..

A true solution is a homogeneous solution in which the solute particles have diameters less than 10 - 7 cm. i.e., the solute particles are of molecular dimensions. The particles are invisible even under powerful microscopes. For example, sodium chloride in water is a true solution. Most i..

Nitrogen is used in high temperature thermometers where mercury cannot be used. This is because mercury boils at 356.7 o C and hence cannot be used in such thermometers. A volume of nitrogen is enclosed in a vessel and introduced into the region of high temperature. Depending upon t..

Liquefaction : When cooled under pressure ammonia condenses to a colorless liquid, which boils at -33.4 o C. When further cooled, it freezes to a white crystalline snow-like solid, which melts at -77.7 o ..

7. If the energy difference between the electronic states of hydrogen atom is 214.68 kJ mol - 1 , what will be the frequency of light emitted when the electron jumps from the higher to the lower energy state? (Planck's constant = 39.79 x 10 - 1 4 kJ mol - 1..