#ssc 10th
- An electric iron of 1000 W is used for 2 hours daily for 30 days. If electricity costs ₹ 5 per unit, the cost is Answer: B. ₹ 300 Energy = 1 kW × 2 h × 30 = 60 kWh (units). Cost = 60 × 5 = ₹ 300 . 1
- An electric generator works on the principle of Answer: C. electromagnetic induction A changing magnetic field linked with a coil induces a current in it. This is electromagnetic induction... 1
- A bulb is rated 100 W, 220 V. Its resistance is Answer: B. 484 Ω R = V²/P = 220²/100 = 48400/100 = 484 Ω. 1
- The average value of the acceleration due to gravity on the surface of the earth is Answer: D. 9.8 m/s² g ≈ 9.8 m/s² on the earth's surface. 1
- 'The line joining a planet and the sun sweeps equal areas in equal intervals of time.' This is Kepler's Answer: C. second law This is Kepler's second law (law of areas). 1
- The weight of a body of mass 50 kg on the earth (g = 9.8 m/s²) is Answer: B. 490 N W = mg = 50 × 9.8 = 490 N. 1
- The number of periods in the modern periodic table is Answer: B. 7 The modern periodic table has 7 periods and 18 groups. 1
- The valency of the element with atomic number 11 is Answer: B. 1 Configuration 2, 8, 1: one valence electron, so the valency is 1 (sodium). 1
- \(\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} + \text{heat}\) is an example of Answer: B. an exothermic reaction Heat is given out, so the reaction is exothermic. 1
- When ethanoic acid reacts with sodium bicarbonate, the gas evolved is Answer: B. carbon dioxide CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂ . 1
- Ethanol reacts with ethanoic acid in the presence of concentrated sulphuric acid to form Answer: A. ethyl ethanoate This esterification reaction gives the ester ethyl ethanoate and water. 1
- The number of structural isomers of butane \(\text{C}_4\text{H}_{10}\) is Answer: A. 2 n-butane (straight chain) and isobutane (2-methylpropane, branched). 1
- The monomer of polythene is Answer: B. ethene Polythene is formed by addition polymerization of ethene ( CH₂=CH₂ ). 1
- \(\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2\) is an example of a Answer: C. combination reaction Two reactants combine to form a single product, so it is a combination reaction. 1
- \(\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}\) is an example of a Answer: D. displacement reaction The more reactive iron displaces copper from copper sulphate solution. 1
- The slow destruction of a metal by the action of air, moisture or chemicals around it is called Answer: A. corrosion This is corrosion; rusting of iron is a common example. 1
- Packets of potato chips are flushed with nitrogen gas to prevent Answer: B. rancidity Nitrogen keeps oxygen away, so the oils and fats in the chips are not oxidised and do not become rancid. 1
- \(\text{AgNO}_3 + \text{NaCl} \rightarrow \text{AgCl} + \text{NaNO}_3\) is an example of a Answer: C. double displacement reaction The ions of the two reactants are exchanged, and white AgCl precipitates. This is double displacemen... 1
- When calcium carbonate is heated strongly, the products formed are Answer: B. CaO and CO₂ CaCO₃ xrightarrowΔ CaO + CO₂ . This is a thermal decomposition reaction. 1
- In the reaction \(\text{CuO} + \text{H}_2 \rightarrow \text{Cu} + \text{H}_2\text{O}\), the substance that is oxidised is Answer: D. H₂ Hydrogen gains oxygen to form water, so it is oxidised. CuO loses oxygen and is reduced. 1
- In the balanced equation \(3\text{Fe} + x\,\text{H}_2\text{O} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2\), the value of \(x\) is Answer: C. 4 Oxygen balance: 4 oxygen atoms in Fe₃O₄ need 4 H₂O ; hydrogen then gives 4H₂ . 1
- Which of the following is an endothermic process? Answer: B. Melting of ice Ice absorbs heat to melt, so it is endothermic. The other three give out heat. 1
- Powdered marble reacts faster with dilute hydrochloric acid than pieces of marble because Answer: B. the powder has a larger surface area Powdering increases the surface area in contact with the acid, which increases the rate of r... 1
- \(\sin^2\theta + \cos^2\theta = \) Answer: D. 1 This is a fundamental trigonometric identity. 1