Archives

Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?

Answer: Metals are minerals or substances that form naturally below the surface of the Earth. Most metals are lustrous or shiny. Metals ate... View Article

Name (a) Three elements that have a single electron in their outermost shells. (b) Two elements that have two electrons in their outermost shells. (c) Three elements with filled outermost shells

Answer: The outermost orbital shell of an atom is called its valence shell. These electrons take part in bonding with other atoms. Electrons in... View Article

Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?

Answer: The chemical reactions of calcium (Ca) and strontium (Sr) are predicted to be similar to those of magnesium (Mg). This is due to the fact... View Article

How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?

Answer: Mendeleev claimed the famous periodic law that “Element properties are a periodic function of their atomic weight.” Mendeleev... View Article

Why do you think the noble gases are placed in a separate group?

Answer: Mendeleev claimed the famous periodic law that “Element properties are a periodic function of their atomic weight.” Mendeleev... View Article

What were the criteria used by Mendeleev in creating his Periodic Table?

Answer: Mendeleev claimed the famous periodic law that “Element properties are a periodic function of their atomic weight.” Mendeleev... View Article

Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (Any two)

Answer: The properties of elements are a periodic function of their atomic masses. It was the discovery of atomic number which led to a change in... View Article

Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements: K, C, AI, Si, Ba.

Answer: In Mendeleev's periodic table, oxygen belongs to group VI A. It has a valency of 2. In the same way, the valencies of all the elements... View Article

What were the limitations of Newlands’ Law of Octaves?

Answer: In the year 1864, the British chemist John Newlands attempted the 62 elements known at that time. He arranged them in ascending order... View Article

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer: Copper, rather than steel or an alloy of iron, is used to make hot water tanks because copper does not react with either water or steam,... View Article

A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Answer: Goldsmith used a solution known as Aqua regia, which is known as royal water in Latin. It's made up of a 3:1 combination of concentrated... View Article

Differentiate between metal and non-metal on the basis of their chemical properties.

Answer: Metals and non-metals are two distinct types of materials that we see every day. Elements can be divided into metals and non-metals and... View Article

You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Answer: Copper reacts with moist carbon dioxide in the air to form copper carbonate, and the shiny brown surface of the copper vessel is covered... View Article

Give reasons: (a) Platinum, gold and silver are used to make jewellery. (b) Sodium, potassium and lithium are stored under oil. (c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking. (d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction

Answer: (a) Platinum, gold and silver are used to make jewellery because the metals used in jewellery are always be chosen on the basis of its... View Article

What type of oxides are formed when non-metals combine with oxygen?

Answer: Metals and non-metals are different kinds of materials that exist surrounding us. Elements can be classified into metals and non-metals... View Article

In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer: Electrolytic refining is a technique that is used for the extraction and purification of metals that are obtained by refining methods.... View Article

Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer: The reactivity series of metals, also known as the activity series, refers to the arrangement of metals in the descending order of their... View Article

You are given a hammer, a battery, a bulb, wires and a switch. (a) How could you use them to distinguish between samples of metals and non-metals? (b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer: (a) How could you use them to distinguish between samples of metals and non-metals? Metals are malleable and can quickly be beaten into... View Article

Food cans are coated with tin and not with zinc because (a) Zinc is costlier than tin. (b) Zinc has a higher melting point than tin. (c) Zinc is more reactive than tin. (d) Zinc is less reactive than tin.

Answer: (c) Zinc is more reactive than tin Zinc has a higher reactivity than tin. Tin interacts only with extremely strong acids. Zinc, on the... View Article

An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be (a) Calcium (b) Carbon (c) Silicon (d) Iron

Answer: (a) Calcium Calcium reacts with oxygen to give calcium oxide. The chemical formula of calcium oxide is CaO. The molecule is formed by... View Article

M	T	W	T	F	S	S
					1	2
3	4	5	6	7	8	9
10	11	12	13	14	15	16
17	18	19	20	21	22	23
24	25	26	27	28	29	30
31