EAMCET Medical EAMCET Medical Solved Paper-2000

  • question_answer
    500 mL of a solution contains 12.6g of oxalic acid (mol. wt. 126). 10 mL of this solution is diluted to 100mL in a flask. What is the molarity (in mol\[{{\text{L}}^{-1}}\]) of the resultant solution?

    A)  0.2                                        

    B)  0.1

    C)  0.02                                      

    D)  0.01

    Correct Answer: C

    Solution :

                     \[\text{Molarity}\,\text{=}\frac{\text{wt}\text{.}}{\text{mol}\text{.wt}\text{. }\!\!\times\!\!\text{ volume in litre}}.\] Mol. Wt. of oxalic acid \[\left( \underset{COOH}{\overset{COOH}{\mathop{|}}}\, \right).2{{H}_{2}}O\] \[=24+64+2+36=126\] Weight of oxalic acid = 12.6 Mol. wt.=126 Volume \[\text{=}\,\text{500}\,\text{mL}\,\text{= }\,\text{0}\text{.5 L}\] \[\text{Malrity}\,\text{=}\,\frac{12.6}{126\times 0.5}=\frac{1}{5}=0.2\] 0.2 M oxalic acid solution. Now, 10 mL of 0.2 M oxalic acid solution is diluted to 100mL solution, than from molarity equation. \[{{M}_{1}}{{V}_{1}}={{M}_{2}}{{V}_{2}}\] \[0.2\times 10={{M}_{2}}\times 100\] \[{{M}_{2}}=\frac{0.2\times 10}{100}=0.02\]


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