Question

Fill in the Blanks:​

Answer 1

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We have to fill in the blanks:

1) Very thin foils of silver (Ag) are used to decorate sweets.

✤ Silver is a highly malleable metal. It is hammered and made into very thin foils which are used for the decoration of sweets. It is also the best conductor of heat and electricity.

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2) Metals get tarnished when to air due to the formation of an oxide layer on the surface.

✤ The shiny surface or the lusturous surface of metals turns dull due to the reaction of metal with oxygen and water vapour in the atmosphere. Copper, Iron, Silver are common metals which gets tarnished easily.

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3) The arrangement of metals in a series, in the decreasing order of their reactivity is called reactivity series.

✤ The Electropositivity of metals determines their relative reactivity. They were experimentally observed and placed in a descending series where H was also added as an exception.

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4) Phosphoric acid is formed dissolving phosphorus pentoxide in water.

✤ The oxide of Phosphorus when reacted with water forms an acid known as Phosphoric acid which is a strong acid. The basicity is 3. It is an Highly exothermic reaction.

Answer 2

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1. Very thin foils of silver(Ag) are used to decorate sweets.

❍ Reason :

Silver is lustrous, soft, very ductile, highly malleable metal. It is an excellent conductor of heat and electricity. Hence it is used to decorate sweets.

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2. Metal get tarnished when exposed to air due to the formation of an oxide layer on it's surface.

❍ Reason :

The lusturous surface of metals turns dull(non-lustrous) or tarnished due to the reaction of metal with oxygen(air) and water vapour(moisture) present in the atmosphere.

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3) The arrangement of metals in a series, in the decreasing order of their reactivity is called reactivity series or electro chemical series.

❍ Reason :

The metals at the top of the reactivity series are powerful reducing agents. The reactivity decreases from the top of the series.

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4) Phosphoric acid is formed dissolving phosphorus pentoxide in water.

❍ Reason :

It reacts with water(H2O) to form phosphoric acid H3PO4. It is highly exothermic and leads to formation of fumes. Diphosphorous Pentoxide is s very powerful dehydrating agent.

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