Phosphorus come in white or red …

The striking surface of the matchbox contains red phosphorus and the head of the matchstick contains potassium chlorate. So when the matchstick is rubbed on the matchbox, some of the red phosphorus is converted to white phosphorus, a chemical i.e. so volatile that it ignites in air.

Metals react with water and produce metal oxides and hydrogen gas. The reaction depends upon the reactivity of metals.

Metals like potassium and sodium react violently with cold water. The reaction of calcium with water is less violent.

Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen.

Metals like aluminium, iron and zinc do not react either with cold or hot water.

But they react with steam to form the metal oxide and hydrogen. Metals such as lead, copper, silver and gold do not react with water at all.

Non-metals do not displace hydrogen because they form negative ions by accepting electrons while hydrogen like metals forms a positive ion.

Therefore metals can displace hydrogen while non-metals cannot.

Highly reactive metals like Sodium reacts with dilute hydrochloric acid according to the following equation:

2Na (s) + 2HCl (aq) → 2NaCl (aq) + H₂ (g)

Hydrogen bubbles will be forming in the solution.

Writing in ionic form:-

2Na (s) + 2H⁺¹ (aq) + 2Cl^-1 (aq) → 2Na⁺¹ (aq) + 2Cl^-1 (aq) + H₂ (g)

Both the sodium atoms are neutral.

But hydrogen on the reactants side has +1 charge whereas in product side it is neutral.

Therefore Na donates one electron to each of hydrogen ion.

Less reactive metals like Zinc reacts with dilute acids.

Zn (s) + 2HCl (aq) → ZnCl₂ (aq) + H₂ (g)
It doesnt matter which metal or which acid is used, if there is a reaction we always get hydrogen gas as well as the salt.

However, how quickly the reaction goes depends on the metal used and how high up in the reactivity series it is.

The term ‘aqua regia’ is Latin for ‘royal water’.

Aqua regia is a very strong acid formed by the combination of concentrated nitric acid and concentrated hydrochloric acid, both of which are strong acids.

It is generally used to remove metals like gold and platinum from substances, especially in microelectronics and micro-fabrications labs.

It is usually a yellow, reddish-orange, fuming liquid and has a rapidly changing composition.

It is primarily popular for its ability to dissolve gold, palladium and platinum, all of which dont react easily with chemicals.

The reason aqua regia can dissolve gold (and metals like platinum and palladium) is that each of its two component acids

(i.e., hydrochloric acid and nitric acid) carries out a different function. While nitric acid is an excellent oxidizing agent, the chloride ions from the HCl form coordination complexes with gold ions, thereby removing them from the solution.

The reduction of the concentration of Au³⁺ ions shifts the equilibrium towards the oxidized form.