KBr contains 32.9% by weight 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.

Potassium crystallizes in a body centred cubic lattice. Calculate the number of unit cells in 1g of potassium. Atomic mass of potassium = 39mu .

An enzyme contain 5.6% Fe, calculate number of Fe atoms present in 1g of enzyme.

Chlorophyll, the green colouring matter of plant contains 2.68% of magnesium by weight. Calculate the number of magnesium atom in 2.0g chlorophyll.

Ice begins to separate at -0.744^@C from a solution containing 2.4 g of non-electrolyte solute in 100 g of water. Calculate the molecular weight of non-electrolyte and osmotic pressure which the solution would exert at 20^@C ?

During the discharge of a lead storage battery, the density of sulphuric acid fell down from 1.294 to 1.139 g/ml. Sulphuric acid of density 1.294g/ml is 39% H_2SO_4 by weight and that of density of 1.139 g/ml is 20% H_2SO_4 by weight. The battery holds 3.5 L of acid and the volume remains practically constant during discharge. calculate the number of ampere hours for which the battery must have been used. The charging and discharging reactions are: Pb^(2+)+SO_4^(2-)LeftrightarrowPbSO_4+2bare(Charging) PbO_2+4H^(+)+SO_4^(2-)+2bareLeftrightarrowPbSO_4+2H2O(Discharging) .

9 moles of "D" and 14 moles of E are allowed to react in a closed vessel according to given reactions. Calculate number of moles of B formed in the end of reaction, if 4 moles of G are present in reaction vessel. (percentage yield of reaction is mentioned in the reaction) Step -1 3D+4E 80%rarr5C+A Step-2 3C+5G 50%rarr 6B+F

Oleum is considered as a solution of SO_(3) in H_(2)SO_(4) , which is obtained by passing SO_(3) in solution of H_(2)SO_(4) When 100 g sample of oleum is diluted with desired mass of H_(2)O then the total mass of H_(2)SO_(4) obtained after dilution is known is known as % labelling in oleum. For example, a oleum bottle labelled as ' 019% H_(2)SO_(4) ' means the 109 g total mass of pure H_(2)SO_(4) will be formed when 100 g of oleum is diluted by 9 g of H_(2)O which combines with all the free SO_(3) present in oleum to form H_(2)SO_(4) as SO_(3)+H_(2)O to H_(2)SO_(4) If excess water is added into a bottle sample labelled as "112% H_(2)SO_(4) " and is reacted with 5.3 g NaCO_(3) then find the volume of CO_(2) evolved at 1 atm pressure and 300 K temperature after the completion of the reaction :

Oleum is considered as a solution of SO_(3) in H_(2)SO_(4) , which is obtained by passing SO_(3) in solution of H_(2)SO_(4) When 100 g sample of oleum is diluted with desired mass of H_(2)O then the total mass of H_(2)SO_(4) obtained after dilution is known is known as % labelling in oleum. For example, a oleum bottle labelled as ' 019% H_(2)SO_(4) ' means the 109 g total mass of pure H_(2)SO_(4) will be formed when 100 g of oleum is diluted by 9 g of H_(2)O which combines with all the free SO_(3) present in oleum to form H_(2)SO_(4) as SO_(3)+H_(2)O to H_(2)SO_(4) 1 g of oleum sample is diluted with water. The solution required 54 mL of 0.4 N NaOH for complete neutralization. The % free SO_(3) in the sample is :

Calculate the molality of a solution containing 20.7g potassium carbonate dissolved in 500ml of solution (assume of density of solution = 1g/ml)

If charge on the electron is 1.60xx10^-19C and 96500 C deposit 107.9g of silver from its solution, calculate the value of Avagadro's number.