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9th Class Science Atoms and Molecules Question Bank Atoms and Molecules

  • question_answer
    A sample of ammonia weighs 4 g. What mass of sulphur dioxide contains the same number of molecules as are in 4 g of ammonia?

    A) 64 g                

    B) 32 g    

    C)        15 g                

    D)        30 g                

    Correct Answer: C

    Solution :

    Mass of ammonia = 4 g Molar mass of ammonia \[(N{{H}_{3}})=17\text{ }g/mol\] \[\therefore \] Number of moles of \[N{{H}_{3}}=\frac{4}{17}mol\] Let mass of sulphur dioxide be \[x\]. Amount of sulphur dioxide \[(S{{O}_{2}})\] \[=\frac{\text{Mass of S}{{\text{O}}_{2}}}{\text{Molar mass of S}{{\text{O}}_{2}}}=\frac{x}{64}\text{mol}\] For equal number of molecules, number of moles should be same. \[\Rightarrow \frac{x}{64}=\frac{4}{17}\Rightarrow x=\frac{4\times 64}{17}=15.05g\approx 15g\]


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