Question

a story on 1. Acids , bases, salts
or
2. Nitrogen

Ans it before 2 Jan 2018

PLZZZZ

Answer 1

 1-

Acids and bases

You will have already learnt quite a lot about acids and bases in Key Stage 3 Science. If you feel a bit rusty on this topic, have a quick look at KS3 Bitesize Chemistry Acids and bases. Here are the bare bones of what you need to know:

Acids

Substances with a pH of less than 7 are acids. The stronger the acid, the lower the pH number. Acids turn blue litmus paper red. They turn universal indicator red if they are strong, and orange or yellow if they are weak.

Bases

Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides. For example, copper oxide and sodium hydroxide ar

Neutral solutions

Neutral solutions have a pH of 7. They do not change the colour of litmus paper, but they turn universal indicator green. Water is neutral.
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2-Nitrogen is a chemical element with symbol Nand atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790, when it was found that nitrogen was present in nitric acid and nitrates. Antoine Lavoisiersuggested instead the name azote, from the Greek άζωτικός "no life", as it is an asphyxiant gas; this name is instead used in many languages, such as French, Russian, and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine

Electrons per shell

2, 5Physical propertiesPhase (at STP)gasMelting point63.15 K ​(−210.00 °C, ​−346.00 °F)Boiling point77.355 K ​(−195.795 °C, ​−320.431 °F)Density (at STP)1.251 g/Lwhen liquid (at b.p.)0.808 g/cm3Triple point63.151 K, ​12.52 kPaCritical point126.192 K, 3.3958 MPaHeat of fusion(N2) 0.72 kJ/molHeat of vaporisation(N2) 5.56 kJ/molMolar heat capacity(N2) 29.124 J/(mol·K)Vapour pressure

P (Pa)1101001 k10 k100 kat T (K)374146536277

Atomic propertiesOxidation states5, 4, 3, 2, 1, −1, −2, −3 ​(a strongly acidic oxide)ElectronegativityPauling scale: 3.04Ionisation energies

1st: 1402.3 kJ/mol2nd: 2856 kJ/mol3rd: 4578.1 kJ/mol




Speed of sound353 m/s (gas, at 27 °C)

Nitrogen is the lightest member of group 15of the periodic table, often called the pnictogens. The name comes from the Greek πνίγειν "to choke", directly referencing nitrogen's asphyxiating properties. It is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N2. Dinitrogen forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycledescribes movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.

Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong triple bond in elemental nitrogen (N≡N), the second strongest bond in any diatomic molecule after carbon monoxide (CO),[2] dominates nitrogen chemistry. This causes difficulty for both organisms and industry in converting N2 into useful compounds, but at the same time means that burning, exploding, or decomposing nitrogen compounds to form nitrogen gas releases large amounts of often useful energy. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems.

Apart from its use in fertilisers and energy-stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric and cyanoacrylate used in superglue. Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules