JEE Main 2019 (Online) 9th January Morning Slot | Environmental Chemistry Question 86 | Chemistry

A water sample has ppm level concentration of the following metals : Fe = 0.2; Mn = 5.0; Cu = 3.0; Zn = 5.0. The metal that makes the water sample unsuitable for drinking is :

JEE Main 2018 (Offline)

MCQ (Single Correct Answer)

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Out of Syllabus

The recommended concentration of fluoride ion in drinking water is up to 1 ppm as fluoride ion is required to make teeth enamel harder by converting
[3Ca₃ (PO₄)₂.Ca(OH)₂] to

[3{Ca(OH)₂}. CaF₂]

[CaF₂]

[3(CaF₂). Ca(OH)₂]

[3Ca₃(PO₄)₂. CaF₂]

JEE Main 2018 (Online) 15th April Evening Slot

MCQ (Single Correct Answer)

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Out of Syllabus

Biochemical Oxygen Demand (BOD) value can be a measure of water pollution caused by the organic matter. Which of the following statements is correct ?

Aerobic bacteria decrease the BOD value.

Anaerobic bacteria increase the BOD value.

Clean water has BOD value higher than 10 ppm.

Polluted water has BOD value higher than 10 ppm.

JEE Main 2017 (Online) 9th April Morning Slot

MCQ (Single Correct Answer)

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Out of Syllabus

Which of the following is a set of greenhouse gases?

CH₄, O₃, N₂, SO₂

O₃, N₂, CO₂, NO₂

O₃, NO₂, SO₂, Cl₂