1. A solution contains 43.5 g of water of NaCl. Determine its percentage by mass. 2. Calculate the molarity of a solution containing 16 g glucose per 300 ml solution.
3. 4o g Sodium Chloride solution contain 5 g of sodium chloride. Determine its percentage by mass.
4. 16 cm3 alcohol is present in 80cm3 of its solution in water. Determine the percentage by volume of alcohol in this solution.
5. Determine the amount of ammonium sulphate (NH4)2SO4 required to prepare 400cm3 of 4M solution. Molar mass of ammonium sulphate is 132.
6. What is the mass in grams of 1 x10^20 atoms of Na?
7. Calculate the molecular mass (in a. m.u) of each of the following substances:
(a) H2O (b) CH6

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chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.

5 structural isomers

the isomers are:

n-exane :   ch3ch2ch2ch2ch2ch3

2-methylpentane :   ch3ch(ch3)ch2ch2ch3

3-methylpentane :   ch3ch2ch(ch3)ch2ch3

2,3-dimethylbutane :   (ch3)2chch(ch3)2

2,2-dimethylbutane :   (ch3)3cch2ch3