JEE Main & Advanced Chemistry Some Basic Concepts of Chemistry Question Bank Atomic Molecular and Equivalent masses

  • question_answer The atomic weights of two elements A and B are 40 and 80 respectively. If x g of A  contains y atoms, how many atoms are present in 2x g of B  

    A)                 \[\frac{y}{2}\]       

    B)                 \[\frac{y}{4}\]

    C)                 y             

    D)                 2y

    Correct Answer: C

    Solution :

               Number of moles of  A\[=\frac{x}{40}\]                    Number of atoms of A\[=\frac{x}{40}\times \text{Avogadro}\ \text{no}\text{.}=y\](say)                    Or \[x=\frac{40y}{\text{Avogadro no}\text{.}}\]                    Number of moles of B\[=\frac{2x}{80}\]                                 Number of atoms of B \[=\frac{2x}{80}\times \text{Av}\text{. no}\text{.}=\frac{2}{80}\times \frac{40y}{\text{Av}\text{. no}\text{.}}\times \text{Av}\text{. no}\text{.}=\text{y}\]

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