| 131. | When the hard water evaporates completely, a white solid remains in the vessel. This is due to the presence of which of the following? 1. Carbonates of Ca and Mg 2. Sulphates of Ca and Mg 3. Chlorides of Ca and Mg Select the correct answer using the codes given below – |
A. 1 and 2 | |
B. 1,2 and 3 | |
C. only 3 | |
D. 1 and 3 |
| 132. | Which of the following is the main harmful gas emitted by automobiles that causes air pollution? |
A. carbon monoxide | |
B. methane | |
C. carbon dioxide | |
D. ozone |
| 133. | Which of the following gas is liquid at the lowest temperature |
A. hydrogen | |
B. oxygen | |
C. helium | |
D. nitrogen |
| 134. | Gunpowder is a mixture of – |
A. Sand and TNT | |
B. TNT and charcoal | |
C. niter, sulfur and charcoal | |
D. sulfur, sand and charcoal |
| 135. | Graphite is used in nuclear reactors |
A. as fuel | |
B. as a lubricant | |
C. as a moderator | |
D. as an insulator |
| 136. | When concentrated H₂SO₄ is added to dry KNO₃, brown fumes are evolved. This smoke is |
A. of SO₃ | |
B. of SO₂ | |
C. of NO₂ | |
D. of N₂O |
| 137. | Which of the following is used to purify drinking water |
A. sulfur dioxide | |
B. chlorine | |
C. florin | |
D. Carbon dioxide |
| 138. | Which of the following is used for dating archaeological finds? |
A. ₉₂U²³⁵ | |
B. ₆C¹⁴ | |
C. ₁H³ | |
D. ₈O¹⁸ |
| 139. | Which element is abundant in the human body? |
A. Carbon | |
B. Iron | |
C. nitrogen | |
D. oxygen |
| 140. | Apart from hydrogen, which other element is found in abundance on the surface of the Sun? |
A. helium | |
B. Neon | |
C. argon | |
D. oxygen |