Heavy water (H₂O₂) and solid graphite is generally used to slow down the speed of neutrons.

Fertilizers are those compounds which provide essential primary nutrients (nitrogen, phosphorus and potassium) required for healthy growth of plants and crops. Nitrogeneous fertilizer provide nitrogen, phosphatic fertilizer provide phosphorus whereas potassh fertilizer provide potassium to soil.
NPK fertilizers are mixed fertilizers. They provide all three essential nutrients (nitrogen, phosphorus and potassium). NPK fertilizers contains nitrogen, phosphorus and potassium in different proportion depending upon the requirement of soil.

Sodium thiosulphate is used in photography as a fixer. It removes Ag from negative by dissolving unexposed silver bromide resulting into formation of complex.
AgBr + 2Na₂S₂O₃ ⟶ Na₃ [Ag(S₂O₃)₂] + NaBr

Steel is an alloy of iron and carbon. On mixing with carbon its strength and toughness got increased. In order to make it further more temperature and abrasion resistant chromium is generally mixed with iron, it also increases its hardness and load bearing capacity. Stainless steel is a category of steel consists (74% Fe, 18% Cr and 8% Ni) is corrosion resistant.

There are 13 essential nutrients required by plants for its healthy and proper growth. Now these nutrients are divided into two categories:
Macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium and sulphur).
Micronutrients (iron, copper, manganese, zinc, boron, molybdenum and chlorine).
Additional mineral nutrient elements which are beneficial but not necessary are sodium, cobalt, vanadium, nickel, solenium, aluminium and silicon. Thus boron, zinc and copper falls into category of essential micronutrients while sodium does not.

Fluorine is the most reactive among all halogens.
However the reactivity decreases from F₂ to I₂ (from top to bottom of group) may be attributed to
(1) Low dissociation enthalpies
(2) High electron affinities

Blue vitriol is blue, crystalline hydrous solution of copper sulphate, CuSO₄•5H₂O, one of the most important industrial copper salts, used in insecticides, germicides, and hair dyes and in the processing of leather and textiles.
Magnesium sulphate is a chemical compound containing magnesium, sulphur and oxygen, with the formula MgSO₄. It is often encountered as the heptahydrate epsomite (MgSO₄.7H₂O), commonly called “Epsom salt”.
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO₃. The salt has many related names such as baking soda, bread soda, cooking soda, bicarbonate of soda.
Caustic soda or sodium hydroxide is an essential ingredient in an array of industrial applications. In addition, consumers use caustic soda when using cleaners, such as oven and drain cleaners.

Potassium bromide is used in photography as a restrainer in black and white developer formulas.
Gun powder, also called black powder, is a mixture of sulphur, charcoal, and potassium nitrate. Gun powder can be made by just using potassium nitrate and charcoal (or alternatively without charcoal), but without the sulphur (or coal), the powder is not as strong.
Potassium sulfate is primarily used as a fertilizer. Mono potassium tartrate is used in bakery by combination with baking soda it results in to evolution of CO₂ which is used for baking cakes.

Coke is added in blast furnance along with iron ore in a blast furnace. Coke being derived from fossil fuel by destructive distillation. Thus it contains higher percentage of carbon and have high calorific value that’s why it functions as a fuel to supply heat. Coke also acts as a reducing agent and reduce metal (iron) oxide to metal.
Chemical equations involved in process are following:
2C(s) + O₂(g) ⟶ 2CO(g)
FeO(s) + CO(g) ⟶ Fe(s) + CO₂(g)
Fe₂O₃ + 3CO(g) ⟶ 2Fe(s) + 3CO₂(g)

Amalgam is an alloy consisting of mercury and any other element.Iron being exceptional in nature not form amalgam with mercury. That’s why mercury is stored in vessels made up of iron. Small quantities of an iron amalgam have, however, been formed by immersing sodium amalgam (containing 1 percent sodium) in a clear, saturated solution of ferrous sulphate.While rest three options zinc,copper and magnesium combine with mercury to form there respective amalgam.

Sodium metal is generally kept inside kerosene oil because of its extreme reactive nature. In open air it reacts violently and burns vigorously to form sodium oxide .

Sulphuric acid (H₂SO₄) reacts very vigorously with water, in a highly exothermic reaction. Thus if you add water to concentrated sulfuric acid, it can boil and you may get a nasty acid burn. That’s why for dilution, acid is added to water not water to acid as specific heat of water is quite large and it can absorb large quantity of heat produced by sulphuric acid. Moreover water is less dense than sulphuric acid, so if you pour water on the acid, the reaction occurs on top of the liquid. If you add the acid to the water, it sinks and any wild and crazy reactions have to get through the water or beaker to get to you.

Diamonds is the polymorph of the element carbon. Calcium is the basic element of naturally occuring marble. Sand is formed by Silicon and Aluminium is the basic element of naturally occurring Ruby.

German silver has a color resembling silver, but is an alloy of primarily copper, nickel and zinc.
Solder is an alloy of tin, antimony, copper and lead. Bleaching powder contains calcium chloride and calcium hypochlorite, used in solution as a bleach. Bleaching powder is sold on the basis of available chlorine, which is liberated when it is treated with a dilute acid. It is used for bleaching paper pulps and fabrics and for sterilizing water.
Hypo solution used in iodometric titration is sodium thiosulphate (Na₂S₂O₃).

Nichrome is a non-magnetic alloy of nickel, chromium, and iron, usually used as a resistance wire. A common alloy is 80% nickel and 20% chromium, by mass. This alloying provide nichrome properties like hardness and ductility.

Anodizing or anodising in British English, is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. The process is called “anodizing” because the part to be treated forms the anode electrode of an electrical circuit. Anodizing increases corrosion and wear resistance. The anodized aluminium layer is grown by passing a direct current through an electrolytic solution, with the aluminium object serving at the anode. The current releases hydrogen at the cathode and oxygen at the surface of the aluminium anode, creating a build up of aluminium oxide layer.

Hardness of water is due to presence of chlorides, sulphates and nitrates of calcium and magnesium. Hard water cannot be used for washing purposes as soap do not form lather with hard water easily which results in to wastage of soap in laundaries. Moreover use of hard water in industries results in to scale formation in inner layers of boilers on which insoluble calcium and magnesium carbonates gets deposited and being a bad conductor of heat result in to wastage of energy. Moreover hard water is not fit for drinking purpose as it hinders ionic imbalance in body. Repeated irrigation of crops by hard water increases calcium and magnesium ions in soil which increases soil alkalinity.

Aqueous solution of copper sulphate is acidic in nature because copper sulphate on dissolving with water, following chemical reaction takes place.
CuSO₄(s) + 2H₂O ⟶ Cu(OH)₂(l) + H₂ SO₄(aq)
Now as we can see in above chemical equation the sulphuric acid generated is strong mineral acid which results into increase in acidity of solution. Thus aqueous solution of copper sulphate is acidic in nature.

The oxidation number characterises the oxidation state of an element in a compound. It is a full number, positive or negative, which indicates the amount of electron loss or gain by this element in the given compound, with respect to the neutral atom. Oxidation number of calcium is 2 in calcium oxide (CaO). Oxidation number of Aluminium is +3 in Sodium aluminium hydride (NaAlH₄) is a chemical compound used as a reducing agent.
Oxidation number of manganese is 4 in Manganese dioxide (MnO₂).
Oxidation number of sulphur is 6 in Pyrosulfuric Acid (H₂S₂O₇).