GK: Class 12 General Q&A · Page 67
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What happens when CaO is added to water
When CaO (calcium oxide or quicklime) is added to water, a highly exothermic and vigorous chemical reaction occurs, producing calcium hydroxide (slaked lime) and releasing substantial heat. The reaction can be so intense that the water boils, steam forms, hissing or crackling sounds are heard, and the solid quicklime swells, fractures, and crumbles into a fine powder or paste. The temperature can rise to 150°C or higher, and if the CaO is added too quickly to water, the violent heat relea
- GeneralClass 12All
What is the classification for this balanced reaction Zn(s) H2SO4(aq) → ZnSO4(aq) + H2(g)
The reaction Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) is classified as a single replacement reaction (single displacement reaction) and simultaneously as a redox reaction. In this reaction, zinc metal replaces hydrogen from sulfuric acid, forming zinc sulfate and hydrogen gas. The single replacement pattern is evident: one element (Zn) displaces another element (H) from a compound (H2SO4), leaving the displaced element as a free substance (H2). From a redox perspective, zinc is oxid
- GeneralClass 12All
What type of reaction is the following CaCO3 → CaO CO2
The reaction CaCO3 → CaO + CO2 is classified as a decomposition reaction (also called a thermal decomposition or breakdown reaction), where a single compound breaks apart into two or more simpler substances when heated. Calcium carbonate decomposes into calcium oxide (quicklime) and carbon dioxide gas when subjected to high temperatures, typically above 800-900°C in industrial kilns. This reaction follows the general decomposition pattern of AB → A + B, where one reactant yields
- GeneralClass 12All
What is the product of the following single replacement reaction Zn 2HCl → ________
The products of the single replacement reaction Zn + 2HCl → are zinc chloride (ZnCl2) and hydrogen gas (H2), giving the complete balanced equation: Zn + 2HCl → ZnCl2 + H2. In this reaction, zinc metal displaces hydrogen from hydrochloric acid because zinc is more reactive than hydrogen on the metal activity series. The zinc atoms lose electrons to form Zn2+ ions that combine with chloride ions to form zinc chloride, while the H+ ions from the acid gain electrons to form H2 gas.
- GeneralClass 12All
How many capitals are there in India
India has one national capital, New Delhi, which serves as the seat of the Union Government and houses Parliament, the Supreme Court, and the offices of the President and Prime Minister. However, India also has 28 state capitals (one for each state) and 8 capitals or administrative centers for its union territories, bringing the total number of capitals or administrative seats to 37. Each state capital houses the state legislative assembly, the chief minister's office, and the high court (tho
- GeneralClass 12All
What is the 1st biggest state
Rajasthan is the largest state in India by area, covering approximately 342,239 square kilometers, which accounts for about 10.4% of India's total geographical area. Located in northwestern India, Rajasthan's vast territory encompasses the Thar Desert, the Aravalli mountain range, and diverse ecological zones ranging from arid deserts to semi-arid scrublands. The state's massive size creates unique administrative challenges, requiring extensive infrastructure networks and decentralized govern
- GeneralClass 12All
Which country has 36 states
Nigeria is the country with 36 states, making it Africa's most populous nation with a federal structure similar in principle to India's state system. Nigeria's 36 states, along with the Federal Capital Territory of Abuja, were created through successive administrative reorganizations designed to accommodate the country's ethnic diversity and improve governance. Each Nigerian state has its own governor, legislature, and administrative structure, operating within a federal framework that balanc
- GeneralClass 12All
Have many states in India
India has 28 states in its current federal structure. This count reflects the most recent administrative configuration following the reorganization of Jammu and Kashmir in 2019. These states represent India's primary subnational political units, each with substantial autonomy to govern matters within state jurisdiction including agriculture, public health, police, local government, and education, while sharing concurrent powers with the central government in areas like criminal law, marriage,
- GeneralClass 12All
Which is the richest state in India
Maharashtra is consistently ranked as India's richest state when measured by Gross State Domestic Product (GSDP), contributing approximately 14-15% of India's total GDP. The state's economic dominance stems from Mumbai—India's financial capital—which houses the Reserve Bank of India, Bombay Stock Exchange, National Stock Exchange, and headquarters of most major banks, financial institutions, and multinational corporations. Maharashtra's economy spans diverse sectors including fina
- GeneralClass 12All
How to balance Ca(OH)2 H2SO4 → CaSO4 H2O
The balanced equation for this acid-base neutralization reaction is Ca(OH)2 + H2SO4 → CaSO4 + 2H2O. The key to balancing this equation lies in recognizing that calcium hydroxide provides two hydroxide ions (OH-) that must react with the two hydrogen ions (H+) from sulfuric acid to form two molecules of water. Start by writing the skeleton equation, then count atoms on each side: calcium and sulfur are already balanced with one atom each, but you have two hydrogen atoms and two oxygen ato
- GeneralClass 12All
What type of reaction is CaO(H2O) → Ca(OH)2
The reaction CaO + H2O → Ca(OH)2 is classified as a combination reaction (also called a synthesis reaction), where two or more reactants unite to form a single, more complex product. Specifically, this is also a hydration reaction, as water is being added to a compound to form a new substance. The reaction demonstrates classic combination reaction characteristics: multiple reactants (calcium oxide and water) merging to create one product (calcium hydroxide) without any byproducts. <
- GeneralClass 12All
Is Ca(OH)2 H2SO4 → CaSO4 2H2O a single replacement reaction
No, the reaction Ca(OH)2 + H2SO4 → CaSO4 + 2H2O is not a single replacement reaction—it is a double displacement reaction (also called a double replacement or metathesis reaction). In this reaction, the positive and negative ions of two different compounds exchange partners to form two entirely new compounds. Specifically, the calcium ion (Ca2+) from calcium hydroxide swaps with the hydrogen ions (H+) from sulfuric acid, resulting in calcium sulfate and water. Single replac
- GeneralClass 12All
Which coefficients correctly balance the formula equation __ CaO __ H2O --> __ Ca(OH)2
The correct coefficients to balance this equation are 1, 1, and 1, which means the equation CaO + H2O → Ca(OH)2 is already balanced without needing any coefficients other than the implied "1" in front of each substance. When checking atom counts, you'll find one calcium atom on each side, two oxygen atoms on each side (one from CaO and one from H2O on the left; two in Ca(OH)2 on the right), and two hydrogen atoms on each side. This reaction represents one of the simplest stoichio
- GeneralClass 12All
How to know if a chemical reaction is single replacement
A chemical reaction is a single replacement (single displacement) if one element replaces another element in a compound, following the general pattern A + BC → AC + B or A + BC → BA + C, where a free element switches places with an element in a compound. The key identifier is that you start with one free element and one compound on the reactant side, and you end with a different free element and a different compound on the product side. For example, in Zn + CuSO4 → ZnSO4 + Cu,
- GeneralClass 12All
What type of reaction takes place when calcium oxide reacts with water
When calcium oxide reacts with water, a combination reaction (synthesis reaction) occurs, specifically categorized as an exothermic hydration reaction. Two reactants—solid calcium oxide and liquid water—unite to form a single product, calcium hydroxide, while releasing substantial heat energy. This reaction exemplifies how metal oxides interact with water to form metal hydroxides, following the general pattern of metal oxide plus water yielding metal hydroxide. The reactio
- GeneralClass 12All
What are the products from the following single replacement reaction Zn(s) + CuSO4(aq)
The products from the single replacement reaction Zn(s) + CuSO4(aq) are zinc sulfate (ZnSO4) and copper metal (Cu), giving the balanced equation: Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s). In this reaction, zinc metal displaces copper from copper sulfate solution because zinc is more reactive than copper according to the metal activity series. The reaction proceeds as zinc atoms lose electrons (are oxidized) to form Zn2+ ions, while Cu2+ ions gain electrons (are reduced) to form solid copper
- GeneralClass 12All
What type of reaction is Ca(OH)2 HCl → CaCl2 H2O
The reaction Ca(OH)2 + 2HCl → CaCl2 + 2H2O is classified as a double displacement reaction (double replacement reaction), and more specifically, it's an acid-base neutralization reaction. In this reaction, the calcium ion (Ca2+) from calcium hydroxide exchanges places with the hydrogen ions (H+) from hydrochloric acid, forming calcium chloride salt and water. The characteristic pattern of double displacement reactions—where positive and negative ions from two compounds swap partner
- GeneralClass 12All
What type of chemical reaction is C6H12O6 6O2 → 6CO2 6H2O
The reaction C6H12O6 + 6O2 → 6CO2 + 6H2O represents cellular respiration, which is classified as a combustion reaction and, more specifically, a complete oxidation reaction. In this process, glucose (a simple sugar) reacts with oxygen to produce carbon dioxide, water, and energy in the form of ATP. From a chemical classification standpoint, this is an exothermic redox reaction where glucose is oxidized (loses electrons) and oxygen is reduced (gains electrons), breaking high-energy C-H an
- GeneralClass 12All
Can CaO dissolve in water
Calcium oxide doesn't truly dissolve in water in the conventional sense—instead, it reacts vigorously with water in an exothermic chemical reaction to form calcium hydroxide, Ca(OH)2. When you add CaO to water, you're not creating a solution of calcium oxide; you're triggering a chemical transformation. The process involves the CaO breaking apart and bonding with water molecules to create an entirely different compound, accompanied by significant heat release and often steam formation.
- GeneralClass 12All
What happens when calcium oxide reacts with water
When calcium oxide (quicklime) reacts with water, it undergoes a vigorous exothermic reaction that produces calcium hydroxide (slaked lime) and releases substantial heat—enough to boil the water in some cases. The reaction is immediate and dramatic, often accompanied by hissing sounds, steam formation, and the material swelling or crumbling as the solid CaO transforms into a white powder or paste. This process, called slaking, can raise temperatures to 150°C or higher, making it ess