27 g of Al (at mass = 27) will react with oxygen equal to


Correct option is

24 g


4 Al     +      3 O2        →           2 Al2O3




How many molecules are there in 10 litres of gas at a pressure of 75 cm at 27 degree Celsius? 


Potassium bromide, KBr contains 32.9% by mass of potassium. If 6.40 g of bromine reacts with 3.60 g of potassium, calculate the number of moles of potassium which combine with bromine to from KBr.


Two acids H2SO4 and H3PO4 are neutralized separately by the same amount of an alkali when sulphate and dihydrogen orthophosphate are formed respectively. Find the ratio of the masses of H2SO4  and 



10 mL of HCl solution gave 0.1435 g of AgCl when treated with excess of AgNO3. Find the normality of the acid solution


A sample of hard water contains 20 mg of Ca2+ ions per litre. How manymilliequivalents of Na2CO3 would be required to soften 1 litre of the sample?


A plant virus is found to consist of uniform cylindrical particles of 150 Å in diameter and 5000 Å long. The specific volume of the virus is 0.75 cm3/ g. If the virus is considered to be a sample particle, find its molecular weight.


The formula weight of an acid is 82.0 in a titration 100 cm3 of a solution of this acid containing 39.0 g of the acid per litre were completelyneutralised by 95.0 cm3 of aqueous NaOH containing 40 .0 g of NaOHper litre. What is the basicity of the acid?


An analysis of a pyrex glass showed 12.9% B2O3, 2.2% Al2O3, 3.8% Na2O, 0.4% K2O and remaining is SiO2. What is the ratio of Si to B atoms in the glass?


One litre of a gas is at a pressure of 10–6 mm of Hg at 25oC. How many molecules are present in the vessel?


2.76 g of silver carbonate (at mass of Ag = 108) on being heated strongly yields a residue weighing