1. Which type of reaction is natural gas combustion an example of?
<p>Natural gas combustion is an example of an exothermic reaction. In an exothermic reaction, energy is released in the form of heat. When natural gas (primarily methane, CH₄) burns, it reacts with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O), and releases heat energy:</p>
<p><span class="mord">CH<sub>4</sub><span class="vlist-s"></span><span class="mbin">+</span>2O<sub>2</sub><span class="vlist-s"></span><span class="mrel">→</span>CO<sub>2</sub><span class="vlist-s"></span><span class="mbin">+</span>2H<sub>2</sub><span class="vlist-s"></span>O<span class="mbin">+</span>heat</span></p>
<p>The release of heat during the combustion process characterizes it as an exothermic reaction.</p>
2. The white powder produced when a magnesium ribbon is burnt in the air is —
When magnesium ribbon is burned in the air, it reacts with oxygen to form magnesium oxide. The white powder produced is magnesium oxide (MgO). The reaction can be represented as:
2Mg+O2(oxygen)→2MgO
3. An example of which of the following reactions is the reaction that produces burnt lime by heating lime-
4. What color of skin falls on the surface of the copper material when the copper corrosion occurs?
<p>When copper corrodes, it forms a green patina on its surface due to the formation of copper carbonate and copper chloride.</p>
<p>This green color is commonly seen on weathered copper surfaces, such as those on old copper roofs and statues.</p>
5. What color of skin on the surface of the silver is caused by the erosion of the silver?
The black coloration on the surface of silver due to erosion is typically caused by the formation of silver sulfide (Ag₂S) as a result of silver reacting with sulfur compounds in the air. This reaction leads to tarnishing, which appears as a black layer on silver items.
6. The basis for verifying a jumping equation is-
The basis for verifying a jumping equation is the law of conservation of energy, not the law of mass. This principle states that energy cannot be created or destroyed, only transformed.
During a jump, chemical energy from muscles converts into kinetic energy as a person leaves the ground, and then into gravitational potential energy as they rise.
At the apex, kinetic energy is minimal and potential energy is maximal. As the person descends, potential energy converts back into kinetic energy.
Thus, energy transformations during a jump are explained by the law of conservation of energy, ensuring that total mechanical energy remains constant.
7. When pieces of zinc are dropped into copper sulphate solution, zinc sulphate and copper are produced. This reaction is an example of which of the following reactions–
<p>The reaction you described, where zinc pieces are added to copper sulfate solution producing zinc sulfate and copper, is an example of a <strong>single displacement reaction</strong>.</p>
<p>Here's the reaction in detail: </p>
<p class="MsoNormal"><span class="mord">Zn (s)</span><span class="mbin">+</span><span class="mord">CuSO<sub>4</sub></span><span class="vlist-s"></span><span class="mord">(aq)</span><span class="mrel">→</span><span class="mord">ZnSO<sub>4</sub></span><span class="vlist-s"></span><span class="mord">(aq)</span><span class="mbin">+</span><span class="mord">Cu (s)</span></p>
<p>In a single displacement reaction, one element replaces another in a compound.</p>
<p>The options you provided are:</p>
<p>(a) Removal<br>(b) Subduction<br>(c) Double removal<br>(d) Addition</p>
<p>None of these options directly correspond to the correct term, which is "single displacement reaction." However, if you must choose from the given options, none accurately describe the reaction. The most closely related term would be "removal" (a), though it is not a standard term for this type of reaction.</p>
8. A ribbon of magnesium should be cleaned before combustion in air —
Magnesium ribbon needs to be cleaned before combustion in air because it often has a thin layer of magnesium oxide on its surface.
This oxide layer can inhibit the reaction of magnesium with oxygen when it is heated.
By cleaning the ribbon, you remove this oxide layer, allowing the magnesium to react more readily with the oxygen in the air during combustion.
9. Adding water to calcium oxide –
<div class="flex-1 overflow-hidden">
<div class="h-full">
<div class="react-scroll-to-bottom--css-wryji-79elbk h-full">
<div class="react-scroll-to-bottom--css-wryji-1n7m0yu">
<div class="flex flex-col text-sm md:pb-9">
<article class="w-full text-token-text-primary focus-visible:outline-2 focus-visible:outline-offset-[-4px]" dir="auto" tabindex="0" data-testid="conversation-turn-13" data-scroll-anchor="true">
<div class="text-base py-[18px] px-3 md:px-4 m-auto md:px-5">
<div class="mx-auto flex flex-1 gap-4 text-base md:gap-5 lg:gap-6 md:max-w-3xl">
<div class="group/conversation-turn relative flex w-full min-w-0 flex-col agent-turn">
<div class="flex-col gap-1 md:gap-3">
<div class="flex max-w-full flex-col flex-grow">
<div class="min-h-[20px] text-message flex w-full flex-col items-end gap-2 break-words [.text-message+&]:mt-5 overflow-x-auto whitespace-pre-wrap" dir="auto" data-message-author-role="assistant" data-message-id="be0cfbcd-a76b-4e2b-aafe-394ded24fa63">
<div class="flex w-full flex-col gap-1 empty:hidden first:pt-[3px]">
<div class="markdown prose w-full break-words dark:prose-invert light">
<p>Explanation for each statement:</p>
<p>(i) <strong>The temperature of the mixture increases.</strong></p>
<ul>
<li><strong>True.</strong> Adding water to calcium oxide (quicklime) is an exothermic reaction, meaning it releases heat, so the temperature of the mixture does increase.</li>
</ul>
<p>(ii) <strong>The temperature of the mixture remains the same.</strong></p>
<ul>
<li><strong>False.</strong> The temperature does not remain the same; it increases due to the exothermic nature of the reaction.</li>
</ul>
<p>(iii) <strong>Calcium hydroxide is produced.</strong></p>
<ul>
<li><strong>True.</strong> The reaction between calcium oxide and water produces calcium hydroxide.</li>
</ul>
<p>(iv) <strong>A thermophilic reaction takes place.</strong></p>
<ul>
<li><strong>False.</strong> "Thermophilic" generally refers to organisms that thrive in high temperatures, not to chemical reactions. The reaction is exothermic, not specifically "thermophilic."</li>
</ul>
<p>Thus, the correct statements are (i) and (iii), making option (a) the correct choice.</p>
</div>
</div>
</div>
</div>
<div class="mt-1 flex gap-3 empty:hidden -ml-2">
<div class="items-center justify-start rounded-xl p-1 flex">
<div class="flex items-center"><button class="rounded-lg text-token-text-secondary hover:bg-token-main-surface-secondary"></button>
<div class="flex items-center pb-0">
<div class="[&_svg]:h-full [&_svg]:w-full icon-md h-4 w-4"> </div>
</div>
<span class="" data-state="closed"><button id="radix-:r1p:" class="cursor-pointer h-[30px] rounded-md px-1 text-token-text-secondary hover:bg-token-main-surface-secondary" type="button" aria-haspopup="menu" aria-expanded="false" data-state="closed"></button></span></div>
</div>
</div>
<div class="pr-2 lg:pr-0"> </div>
<div class="mt-3 w-full empty:hidden">
<div class="text-center"> </div>
</div>
</div>
<div class="absolute">
<div class="flex items-center justify-center"> </div>
</div>
</div>
</div>
</div>
</article>
</div>
</div>
</div>
</div>
</div>
<div class="md:pt-0 dark:border-white/20 md:border-transparent md:dark:border-transparent w-full">
<div class="text-base px-3 md:px-4 m-auto md:px-5">
<div class="mx-auto flex flex-1 gap-4 text-base md:gap-5 lg:gap-6 md:max-w-3xl"><form class="w-full" aria-haspopup="dialog" aria-expanded="false" aria-controls="radix-:r1:" data-state="closed">
<div class="relative flex h-full max-w-full flex-1 flex-col">
<div class="absolute bottom-full left-0 right-0 z-20"> </div>
<div class="group relative flex w-full items-center">
<div class="flex w-full flex-col gap-1.5 rounded-[26px] p-1.5 transition-colors bg-[#f4f4f4] dark:bg-token-main-surface-secondary">
<div class="flex items-end gap-1.5 md:gap-2">
<div class="flex min-w-0 flex-1 flex-col pl-4"> </div>
</div>
</div>
</div>
</div>
</form></div>
</div>
</div>
10. The velvety fumes emitted when lead nitrate is heated are:
<p class="MsoNormal">When lead nitrate (<span class="katex-mathml">Pb(NO<sub>3</sub>)<sub>2</sub> </span>is heated, it decomposes and produces several gases and solid products. The main products of this decomposition are:</p>
<p class="MsoNormal" style="margin-bottom: .0001pt; line-height: normal;"><span style="font-size: 12.0pt; font-family: Symbol; mso-ascii-font-family: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman';">·</span><span style="font-size: 12.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';"><span style="mso-spacerun: yes;"> </span>Lead(II) oxide (PbO)</span></p>
<p class="MsoNormal" style="margin-bottom: .0001pt; line-height: normal;"><span style="font-size: 12.0pt; font-family: Symbol; mso-ascii-font-family: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman';">·</span><span style="font-size: 12.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';"><span style="mso-spacerun: yes;"> </span>Nitrogen dioxide (NO<sub>2</sub>)</span></p>
<p class="MsoNormal"><span style="font-size: 12.0pt; line-height: 115%; font-family: Symbol; mso-ascii-font-family: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-bidi-font-family: 'Times New Roman';">·</span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';"><span style="mso-spacerun: yes;"> </span>Oxygen (O<sub>2</sub>)</span></p>
<p class="MsoNormal">The decomposition reaction can be represented as:</p>
<p class="MsoNormal"><span class="mord">2 Pb(NO<sub>3</sub></span><span class="vlist-s"></span><span class="mord">)<sub>2</sub></span><span class="vlist-s"></span><span class="mrel">→</span><span class="mord">2 PbO</span><span class="mbin">+</span><span class="mord">4 NO<sub>2</sub></span><span class="vlist-s"></span><span class="mbin">+</span><span class="mord">O<sub>2</sub></span><span class="vlist-s"></span></p>
<p class="MsoNormal">So, the brown-colored gases produced are primarily nitrogen dioxide (<span class="katex-mathml">NO<sub>2</sub></span><span class="vlist-s"></span>).</p>
11. What happens when light hydrochloric acid is added to iron powder ?
<p>When dilute hydrochloric acid is added to iron filings, the reaction produces hydrogen gas and iron chloride. The chemical equation for the reaction is:</p>
<p class="MsoNormal"><span class="mord">Fe (s)</span><span class="mbin">+</span><span class="mord">2HCl (aq)</span><span class="mrel">→</span><span class="mord">FeCl<sub>2</sub></span><span class="vlist-s"></span><span class="mord">(aq)</span><span class="mbin">+</span><span class="mord">H<sub>2</sub></span><span class="vlist-s"></span><span class="mord">(g)</span></p>
<p>Here’s what happens:</p>
<ul>
<li style="list-style-type: none;">
<ul type="disc">
<li class="MsoNormal" style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><strong><span style="font-size: 12.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';">Hydrogen gas</span></strong><span style="font-size: 12.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';"> (H<sub>2</sub>) is evolved.</span></li>
<li class="MsoNormal" style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; line-height: normal; mso-list: l0 level1 lfo1; tab-stops: list .5in;"><strong><span style="font-size: 12.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';">Iron chloride</span></strong><span style="font-size: 12.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman';"> (FeCl<sub>2</sub>) is formed.</span></li>
</ul>
</li>
</ul>
12. Which of the following is characteristic of a chemical reaction ?
During a chemical reaction, changes in state, color changes, and the evolution of gas can all occur simultaneously. These are characteristic features of a chemical reaction.
13. Fe2 O3 +2AI → The above reaction is an example –
<p>The reaction Fe₂O₃ + 2Al → is an example of a displacement reaction, where aluminum displaces iron from iron(III) oxide, forming aluminum oxide and iron. This type of reaction is also known as a thermite reaction.</p>
14. Which of the statements are incorrect for the following reaction? (i) The lead is disturbed. (ii) Carbon dioxide is released. (iii) Carbon is emitted. (iv) Lead oxide is dissolved.
<p>The statements "(i) The lead is disturbed" and "(ii) Carbon dioxide is released" are incorrect for the given reaction. This would mean that the other statements are correct, and the incorrect statements are those related to lead being "disturbed" and the release of carbon dioxide.</p>
15. Which of the following is not an addition reaction?
<p>The reaction (c) CH₄ + 2O₂ → CO₂ + 2H₂O is not an addition reaction; it is a combustion reaction.</p>
<p>In this process, methane (CH₄) reacts with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O).</p>
<p>Combustion reactions involve a fuel reacting with oxygen to release energy, typically in the form of heat and light, along with producing products like CO₂ and H₂O.</p>
<p>In contrast, an addition reaction involves two or more reactants combining to form a single product, as seen in the other options where substances combine without breaking down into multiple products.</p>
16. Electrolysis of water Which of the following reactions is an example of-
<p>Electrolysis of water is a decomposition reaction where water (H₂O) is broken down into its constituent elements, hydrogen (H₂) and oxygen (O₂), using an electric current.</p>
<p>This process involves the separation of water molecules into hydrogen gas and oxygen gas, making it a clear example of a decomposition reaction, not an addition, removal, or thermoelectric process.</p>
17. ZnO + C → Zn + CO In this reaction, the two oxidized and deoxidized substances are –
<p>In the reaction ZnO + C → Zn + CO, zinc oxide (ZnO) is reduced to zinc (Zn), and carbon (C) is oxidized to carbon monoxide (CO).</p>
<p>Therefore, the substances undergoing oxidation and reduction are carbon (C) and zinc oxide (ZnO), respectively.</p>
18. errous sulfate is produced in thermal decomposition. –
<p>When ferrous sulfate (FeSO₄) undergoes thermal decomposition, it breaks down to produce sulfur dioxide (SO₂), sulfur trioxide (SO₃), and ferric oxide (Fe₂O₃). The reaction is as follows:</p>
<p class="MsoNormal"><span class="mord">2FeSO<sub>4</sub></span><span class="vlist-s"></span><span class="mrel">→</span><span class="mord">Fe<sub>2</sub></span><span class="vlist-s"></span><span class="mord">O<sub>3</sub></span><span class="vlist-s"></span><span class="mbin">+</span><span class="mord">SO<sub>2</sub></span><span class="vlist-s"></span><span class="mbin">+</span><span class="mord">SO<sub>3</sub></span><span class="vlist-s"></span></p>
<p>This indicates that all the products listed in the options (SO₂, SO₃, and Fe₂O₃) are formed during the thermal decomposition of ferrous sulfate, making "(d) All of the above" the correct choice.</p>
19. Which of the following is a thermal dissociation reaction?
<p>This reaction is an example of <strong>thermal dissociation</strong> (or <strong>thermal decomposition</strong>). In this reaction, calcium carbonate (CaCO₃) decomposes into calcium oxide (CaO) and carbon dioxide (CO₂) when heated. This type of reaction involves breaking down a compound into simpler substances due to the application of heat.</p>
<p>The other reactions listed are also decomposition reactions but involve different conditions:</p>
<ul>
<li>(a) 2AgCl → 2Ag + Cl₂ is the thermal decomposition of silver chloride.</li>
<li>(b) 2H₂O → 2H₂ + O₂ is the electrolysis of water.</li>
<li>(c) 2AgBr → 2Ag + Br₂ involves the decomposition of silver bromide, often under light.</li>
</ul>
20. Mixing a solution of sodium sulphate and barium chloride – (i) Sodium chloride and barium sulphate are produced. (ii) A dissociation reaction takes place. (iii) A Hi removal reaction takes place. (iv) A precipitation reaction takes place.
<div class="flex-1 overflow-hidden">
<div class="h-full">
<div class="react-scroll-to-bottom--css-vnrnw-79elbk h-full">
<div class="react-scroll-to-bottom--css-vnrnw-1n7m0yu">
<div class="flex flex-col text-sm md:pb-9">
<article class="w-full text-token-text-primary focus-visible:outline-2 focus-visible:outline-offset-[-4px]" dir="auto" tabindex="0" data-testid="conversation-turn-45" data-scroll-anchor="true">
<div class="text-base py-[18px] px-3 md:px-4 m-auto md:px-5">
<div class="mx-auto flex flex-1 gap-4 text-base md:gap-5 lg:gap-6 md:max-w-3xl lg:max-w-[40rem] xl:max-w-[48rem]">
<div class="group/conversation-turn relative flex w-full min-w-0 flex-col agent-turn">
<div class="flex-col gap-1 md:gap-3">
<div class="flex max-w-full flex-col flex-grow">
<div class="min-h-[20px] text-message flex w-full flex-col items-end gap-2 break-words [.text-message+&]:mt-5 overflow-x-auto whitespace-pre-wrap" dir="auto" data-message-author-role="assistant" data-message-id="ad1b7327-83a9-4b71-a370-3af37d0be895">
<div class="flex w-full flex-col gap-1 empty:hidden first:pt-[3px]">
<div class="markdown prose w-full break-words dark:prose-invert light">
<ul>
<li>
<p><strong>(i) Sodium chloride and barium sulfate are produced.</strong><br>When a solution of sodium sulfate (Na₂SO₄) is mixed with barium chloride (BaCl₂), barium sulfate (BaSO₄) precipitates out of the solution, and sodium chloride (NaCl) remains in the solution. </p>
<p class="MsoNormal">The reaction is: <span class="katex-mathml">Na<sub>2</sub>SO<sub>4</sub>+BaCl<sub>2</sub>→BaSO<sub>4</sub> (precipitate)+2NaCl</span></p>
</li>
<li>
<p><strong>(ii) A dissociation reaction takes place.</strong><br>Dissociation reactions involve the breaking down of ionic compounds into their ions when dissolved in water. While dissociation occurs in solution, it is not the primary reaction in this context.</p>
</li>
<li>
<p><strong>(iii) A Hi removal reaction takes place.</strong><br>This statement is unclear. If "Hi removal" refers to the removal of ions from solution due to precipitation, then it is relevant. However, "Hi removal" is not a standard term in chemistry.</p>
</li>
<li>
<p><strong>(iv) A precipitation reaction takes place.</strong><br>This is the key reaction observed. Barium sulfate forms a precipitate, which is an example of a precipitation reaction.</p>
</li>
</ul>
<p>Thus, the primary processes involved are the formation of products (sodium chloride and barium sulfate), the occurrence of a precipitation reaction, and potentially some confusion about "Hi removal," making <strong>(d) (i), (iii), (iv)</strong> the best option.</p>
</div>
</div>
</div>
</div>
<div class="mt-3 w-full empty:hidden"> </div>
</div>
<div class="absolute"> </div>
</div>
</div>
</div>
</article>
</div>
</div>
</div>
</div>
</div>
21. White seal var chloride will be colored after exposure to sunlight for some time –
White lead chloride (PbCl₂) will turn gray upon exposure to sunlight.
This change in color occurs due to the photochemical decomposition of lead chloride. When exposed to sunlight, PbCl₂ decomposes to form lead(II) oxide (PbO) and chlorine gas (Cl₂), which results in a grayish discoloration of the lead chloride.
22. Which of the following reactions is used in black and white photography?
<p>This reaction involves the photochemical decomposition of silver bromide (AgBr) into silver (Ag) and bromine gas (Br₂) when exposed to light.</p>
<p>Silver bromide is a light-sensitive compound used in photographic films and papers.</p>
<p>The exposure to light causes the silver bromide to decompose, creating a latent image on the film that is later developed to produce a visible photograph.</p>
23. 2Cu + O2 → 2CuO – The two oxidized and deoxidized substances in this reaction are—
In the reaction:
2Cu+O₂→2CuO
Oxidized Substance: Copper (Cu) is oxidized to copper(II) oxide (CuO). In this process, copper loses electrons and its oxidation state increases from 0 in elemental copper to +2 in copper oxide.
Deoxidized Substance: Oxygen (O₂) is reduced to form oxide ions (O²⁻) in copper(II) oxide (CuO). In this process, oxygen gains electrons and its oxidation state decreases from 0 in O₂ to -2 in CuO.
24. Which of the following is not produced in the thermal decomposition of lead nitrate –
<p>In the thermal decomposition of lead nitrate (Pb(NO₃)₂), the reaction produces:</p>
<p class="MsoNormal"><span class="mord">2Pb(NO<sub>3</sub></span><span class="vlist-s"></span><span class="mord">)<sub>2</sub></span><span class="vlist-s"><sub></sub></span><span class="mrel">→</span><span class="mord">2PbO</span><span class="mbin">+</span><span class="mord">4NO<sub>2</sub></span><span class="vlist-s"></span><span class="mbin">+</span><span class="mord">O<sub>2</sub></span><span class="vlist-s"></span></p>
<p><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="mord"><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist-s"><span class="katex-mathml"></span></span></span></span></span></span></span></span></span>The products are:</p>
<ul>
<li>Lead oxide (PbO)</li>
<li>Nitrogen dioxide (NO₂)</li>
<li>Oxygen (O₂)</li>
</ul>
<p>Nitrogen gas (N₂) is <strong>not</strong> produced in this reaction.</p>