CBSE Class X – Science Chemistry Exam (Full Syllabus)

Copper is placed above silver in electrochemical series and thus reaction occurs

Potassium iodide on reacting with lead nitrate gives yellow precipitate of lead iodide.KI + Pb(NO3)2 → PbI2 + KNO3

Acids turn blue litmus solution to red. They have a sour taste as in the case of vinegar and are sticky to touch. On the other hand, bases turn red litmus solution to blue. Bases are bitter in taste as in the case of baking soda and are slippery to touch.

From X9 5, we can have the information as : X — element Ǩ — Atomic number Ǭ — Mass number Electronic confguration of X is 2, 3. Group number is found out on the basis of valance electrons. Valence electrons are 3 so group number is 10 + 3 = 13. Period can be found out by knowing the number of shells

Non-metals form acidic oxides. The element with atomic number Ǫ is a nonmetal (nitrogen). Rest three elements with atomic numbers.

Atomic number 14 (electronic confguration of 2,8,4) is for silicon element, which is a metalloid and exhibit properties of both metal and non-metal

Only 0.03% of atmospheric air contains carbon in the form of carbon dioxide. The natural concentration of  carbon monoxide  in  the air  is around 0.2 parts per million (ppm).

A molecule of ammonia (NH₃) has only single bonds. The atomic number of N is 7. Its electronic configuration is ȷ2, Ǩȸ so it needs 3 more electrons to complete its octet.

Denatured alcohol is the ethyl alcohol which has been made unfit for drinking purpose by adding small amount of poisonous substance like methanol, pyridine, etc.

Aqua-regia is the mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. Aqua-regia, being a strong acid, dissolves gold.

Magnesium metal never reacts with cold water but reacts with both hot water and steam to form magnesium hydroxide and hydrogen gas.

Due to the weaker bond of gallium atoms their melting point is also low.