chemistry for grade 7\\

10. Calculate the average atomic weight of silicon having 92.2% of Si-28 isotope of relative mass 27.98 amu, 4.7% of Si-29 isotope of relative mass 28.98 amu and 3.1% of Si-30 isotope of relative mass 29.97 am..

17. The concentration of Ca + + in blood is 0.0025M. If an oxalate solution with oxalate ion concentration 1 x 10 - 7 M is added to it, state whether precipitation occurs or not. Solubility product of calcium oxalate = 2.3 x 10 - 9..

Magnesium sulphate occurs in nature as, Kieserite MgSO 4 .H 2 O Epsomite MgSO 4 .7H 2 O (in certain gypsum deposits). It is also present in certain mineral sprin..

11. The heats of combustion of CH 4 and C 2 H 6 are -890.3 and -1559.7kJ mol - 1 respectively. Which of the two has greater efficiency of fuel per gra..

This involves the mixing of one s three p and three d-orbitals forming seven sp 3 d 3 hybrid orbitals having pentagonal bipyramidal geometry. The geometry of IF 7 molecule can be explained on the basis of sp 3 d 3 Hybridizatio..

On reaction sodium salt of phenol with carbon dioxide gas, ortho hydroxy benzoic acid is formed as the main product. The temperature is 400 K and a pressure of 4-7 atm is required. Sodium salicylate is formed which an acidification yields salicylic acid (ortho hydroxy benzoic acid)...

Fluorine forms two oxides F 2 O and F 2 O 2 , which are called oxygen fluorides. In this case fluorine is more electronegative than oxygen. On the other hand the oxides of Cl, Br and I are called oxides. They form oxides from + 1 to + 7 oxidation stat..

Micelles are formed by specific molecules which have lyophilic as well as lyophobic ends. Ordinary soap which contains sodium stearate (C 1 7 H 3 5 COONa) forms micelle in water. The stearate ion has a long hydrocarbon end that is hydrophobic (because it is nonpolar) and a polar c..

Borax (Na 2 B 4 O 7 .10H 2 O) - Borax occurs naturally as tincal (contains about 55% borax) in certain inland lakes of India, Tibet and California (U.S.A...

Oxides of Halogens - Fluorine forms two oxides F 2 O and F 2 O 2 , which are called oxygen fluorides. In this case fluorine is more electronegative than oxygen. On the other hand the oxides of Cl, Br and I are called oxides. They form oxides from + 1 to + 7 oxidation stat..