Sunday 31 January 2021

Quiz-Counting Atoms (IGCSE CHEMISTRY)



NAME/#        : __________________________

DAY, DATE        : __________________________        

  1. Calculate the volume of the 3.2 g of sulphur trioxide gas at r.t.p condition and at s.t.p condition


  1.  A sample of carbon monoxide gas, CO, has volume of 6 dm3 at r.t.p.
  1. How many moles of the gas are there in the sample?


  1. How many particles are there


  1. What is the mass of the sample?


  1. An unknown compound is analyzed and found to consist of 24.3 % carbon, 4.1 % hydrogen, and 71.6 % chlorine.  If the molecular mass of the compound is 98.8, what is the molecular formula of the compound?


  1. The element boron forms several compounds that contain only boron and hydrogen. A sample of one of these compounds weighing 56 g was found to contain 44 g of boron.
  1. Find the ratio of the number of hydrogen atoms to the number of boron atoms in the compound.


  1. The rtelative molecular mass of the compound is 28. Write the chemical formula for this compound of boron and hydrogen.


  1. Hydrated sodium carbonate has the formula Na2CO3.nH2O. on strong heating, Hydrated sodium carbonate decomposes completely into water and anhydrous sodium carbonate, CuSO4. The formula of Hydrated sodium carbonate was found by the following procedure.


        A mass of Hydrated sodium carbonate was heated strongly in a crucible until decomposition was complete.


the following result was obtained.

Mass of empty crucible = 11.50 g

Mass of crucible +         hydrated copper(II) sulphate = 17.22 g

Mass of crucible + anhydrous copper(II) sulphate =  13.62 g

  1. Suggest how you could find out when the decomposition of Hydrated sodium carbonate is complete                                                                                


  1. Calculate the mass of water evaporated  in the decomposition, and the number of moles of the water.        


  1. Calculate the mass of anhydrous sodium carbonate produced in the decomposition, and the number of moles of Na2CO3                                                                     


  1. Find the value of n in the formula                                                            


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