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Concentration in ppm

This type of question, asked 3 times: 26 Jul 2022, 30 Jan 2023, 4 Apr 2025. All 4 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    26 Jul 2022

    51
    Chlorophyll extracted from the crushed green leaves was dissolved in water to make 2 L2\text{ }L solution of MgMg of concentration 48ppm48ppm. The number of atoms of MgMg in this solution is x×1020x \times10^{20} atoms. The value of xx is . (Nearest Integer) (Given: Atomic mass of MgMg is 24 g mol−124\text{ }g{\text{ }mol}^{- 1},  NA=6.02×1023 mol−1)\left. \ N_{A}= 6.02 \times10^{23}{\text{ }mol}^{- 1} \right)

  2. Question 2

    30 Jan 2023

    60
    Some amount of dichloromethane (CH2Cl2)\left( CH_{2}Cl_{2} \right) is added to 671.141 mL671.141\text{ }mL of chloroform (CHCl3)\left( CHCl_{3} \right) to prepare 2.6×10−3M2.6 \times10^{- 3}M solution of CH2Cl2CH_{2}Cl_{2} (DCM). The concentration of DCM is ppm (by mass). Given: atomic mass: C=12C = 12
    H=1H = 1
    Cl=35.5Cl = 35.5
    density of CHCl3=1.49 g cm−3CHCl_{3}= 1.49\text{ }g{\text{ }cm}^{- 3}

  3. Question 3

    4 Apr 2025

    48
    Fortification of food with iron is done using FeSO4.7H2O{FeSO}_{4}.7H_{2}O. The mass in grams of the FeSO4.7H2O{FeSO}_{4}.7H_{2}O required to achieve 12 ppm of iron in 150 kg of wheat is (Nearest integer) [Given : Molar mass of Fe, S and O respectively are 56,32 and 16 g mol−116\text{ }g{\text{ }mol}^{- 1} ]

  4. Question 4

    4 Apr 2025

    121
    Sea water, which can be considered as a 6 molar (6M)(6M) solution of NaCl , has a density of 2 g mL−12\text{ }g{\text{ }mL}^{- 1}. The concentration of dissolved oxygen ( O2O_{2} ) in sea water is 5.8 ppm . Then the concentration of dissolved oxygen (O2)\left( O_{2} \right) in sea water, is x×10−4 mx \times 10^{- 4}\text{ }m. x=x = (Nearest integer) Given: Molar mass of NaCl is 58.5 g mol−158.5\text{ }g{\text{ }mol}^{- 1} Molar mass of O2O_{2} is 32 g mol−132\text{ }g{\text{ }mol}^{- 1}