1.
A heavy crystalline solid on heating decrepitates to form a residue that is reddish-brown when hot and yellow when cold. It gives off a brown gas along with oxygen.
Correct Answer
C. Lead nitrate
Explanation
Lead nitrate is the correct answer because it fits the given description. Lead nitrate is a heavy crystalline solid that decrepitates (breaks down) when heated, leaving behind a reddish-brown residue when hot and a yellow residue when cold. It also gives off a brown gas, which is likely nitrogen dioxide (NO2), along with oxygen.
2.
A red solid on heating gives off oxygen. The silvery droplet is seen on the cooler parts of the test tube.
Correct Answer
A. Mercury(II)oxide
Explanation
Mercury(II)oxide is the correct answer because it is a red solid that decomposes upon heating, releasing oxygen gas. The silvery droplet seen on the cooler parts of the test tube is likely mercury, which is a product of the decomposition reaction. This observation is consistent with the properties of mercury(II)oxide.
3.
A chocolate brown solid on heating gives off colorless and odorless gas which rekindles a glowing wooden splinter. The residue is reddish-brown when hot and yellow when cold.
Correct Answer
B. Lead(IV)oxide
Explanation
The given information describes a compound that is a chocolate brown solid, which upon heating gives off a colorless and odorless gas that rekindles a glowing wooden splinter. The residue left behind is reddish-brown when hot and yellow when cold. This behavior is characteristic of lead(IV) oxide.
4.
A white crystalline solid decomposes on explosively on heating and leaves behind no residue. One of the gaseous product formed is neither combustible nor does it supports combustion or turns limewater milky.
Correct Answer
C. Ammonium nitrite
Explanation
Ammonium nitrite is the correct answer because it fits the given description. When heated, it decomposes explosively and leaves behind no residue. One of the gaseous products formed is neither combustible nor does it support combustion or turn limewater milky. This matches the properties of ammonium nitrite, making it the most likely compound in this scenario.
5.
A white crystalline solid sublime on heating to form dense white fumes. The fumes solidify on the cooler parts of the test tube to form the original solid.
Correct Answer
B. Ammonium chloride
Explanation
Ammonium chloride is the correct answer because it fits the description given in the question. Ammonium chloride is a white crystalline solid that sublimes on heating, meaning it changes directly from a solid to a gas without melting. When the gas cools down, it solidifies again on the cooler parts of the test tube, forming the original solid. This process is known as sublimation and is characteristic of ammonium chloride.
6.
An orange-colored crystalline solid on heating leaves behind a greenish mass. It swells and gives off nitrogen and steam.
Correct Answer
A. Ammonium dichromate
Explanation
Ammonium dichromate fits the given description because it is an orange-colored crystalline solid that decomposes upon heating, leaving behind a greenish mass. The decomposition of ammonium dichromate produces nitrogen gas and steam.
7.
A solid which is yellow when hot and white when cold
Correct Answer
B. Zinc oxide
Explanation
Zinc oxide is the correct answer because it exhibits a phenomenon known as thermochromism. When heated, zinc oxide turns yellow due to the movement of electrons within the crystal lattice. As it cools down, the electrons return to their original positions, causing the zinc oxide to turn back to its white color. This property makes zinc oxide suitable for various applications, including as a pigment in paints and as a UV filter in sunscreens.
8.
A white crystalline solid melts on heating. It gives off a colorless gas that rekindles the glowing splinter. The paste of solid in HCl gives a golden-yellow flame, when held in a non-luminous flame.
Correct Answer
B. Sodium nitrate
Explanation
Sodium nitrate is the correct answer because it matches all the given observations. Sodium nitrate is a white crystalline solid that melts when heated. When it melts, it gives off a colorless gas that can rekindle a glowing splinter, indicating the presence of oxygen. When a paste of sodium nitrate is mixed with hydrochloric acid (HCl), it produces a golden-yellow flame when held in a non-luminous flame. This is due to the presence of sodium ions in sodium nitrate, which emit a characteristic yellow color when heated.
9.
A light green solid on heating gives off a black residue and gives off a colorless gas which turns lime water milky.
Correct Answer
B. Copper (II)carbonate
Explanation
Copper (II) carbonate is the correct answer because when heated, it decomposes to form black copper (II) oxide residue and releases carbon dioxide gas, which turns lime water milky due to the formation of calcium carbonate.
10.
A white crystalline solid decomposes explosively on heating and leaves behind no residue. One of the gaseous products formed is a supporter of combustion.
Correct Answer
A. Ammonium nitrate
Explanation
Ammonium nitrate is a white crystalline solid that decomposes explosively on heating and leaves behind no residue. One of the gaseous products formed during its decomposition is nitrogen dioxide, which is a supporter of combustion. Therefore, ammonium nitrate is the correct answer.