3 these are 5,6&7 are the significant
Agar is used to assist establish an anaerobic environment that promotes nitrate reduction.
Nitrate Reduction test:
- The nitrate in the broth is converted to nitrite by organisms that can produce the nitrate reductase enzyme, which can then be further converted to nitric oxide, nitrous oxide, or nitrogen.
- Anaerobic respiration and denitrification are two processes that can convert nitrate to a variety of compounds.
- While denitrification only reduces nitrate to molecular nitrogen, anaerobic respiration employs nitrate as the bacterium's final electron acceptor, reducing it to a range of chemicals.
- The nitrate reduction test is based on the detection of nitrite and its capacity to produce a red precipitate (prontosil), which is a water-soluble azo dye, when it combines with sulfanilic acid to create a complex (nitrite-sulfanilic acid).
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The mass of MgCl₂ produced is 5.685 grams.
<h3>What is mass?</h3>
Mass is the quantity of matter of a physical body.
The reaction is
Mg + 2HCl → MgCl₂ + H₂
2 mole of HCl
(2 × 36.458) = 72.8 g
1 moles of MgCl₂
(1 × 95.21 g) = 95.21 g
1 g Mg will produce = 
4.67 mol Mg will produce

Thus, the mass of MgCl₂ produced is 5.685 grams.
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Nuclear binding energy is the energy that would be required to disassemble the nucleus of an atom into its component parts. These component parts are netrons and protons, which are collectively called nucleons