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Some Basic Concepts of Chemistry question

2021 · 20 Jul · Shift 2 · Q20
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Some Basic Concepts of Chemistry question

2021 · 20 Jul · Shift 2 · Q20

JEE MainChemistrySome Basic Concepts of ChemistryNumerical+4 / −1
4g equimolar mixture of NaOHNaOHNaOH and Na2CO3Na_2CO_3Na2​CO3​ contains x g of NaOHNaOHNaOH and y g of Na2CO3Na_2CO_3Na2​CO3​. The value of x is ‾\underline{\hspace{2cm}}​ g. (Nearest integer)
Numerical answer
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Correct answer: 1

  1. Let the number of moles of NaOHNaOHNaOH and Na2CO3Na_2CO_3Na2​CO3​ each be nnn.

    Since the mixture is equimolar, both substances have equal moles.

  2. Write the mass expressions:

    • Molar mass of NaOH=23+16+1=40 g/molNaOH = 23 + 16 + 1 = 40\,g/molNaOH=23+16+1=40g/mol
    • Molar mass of Na2CO3=2(23)+12+3(16)=106 g/molNa_2CO_3 = 2(23) + 12 + 3(16) = 106\,g/molNa2​CO3​=2(23)+12+3(16)=106g/mol

    Hence, x=40nx = 40nx=40n y=106ny = 106ny=106n

  3. Total mass of mixture is 4 g4\,g4g:

    x+y=4x + y = 4x+y=4 40n+106n=440n + 106n = 440n+106n=4 146n=4146n = 4146n=4 n=4146=273n = \frac{4}{146} = \frac{2}{73}n=1464​=732​

  4. Now calculate xxx:

    x=40n=40(273)=8073≈1.096 gx = 40n = 40\left(\frac{2}{73}\right) = \frac{80}{73} \approx 1.096\,gx=40n=40(732​)=7380​≈1.096g

  5. Nearest integer value of xxx:

    x≈1 gx \approx 1\,gx≈1g

Therefore, the required value is 111.

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