Chemical Reactions and Equations: Class 10 Science Q&A
29 free answers on Chemical Reactions and Equations (Science) for Class 10 students, across CBSE, ICSE and State boards. Includes questions such as “What is hybridization? What are its types, with an example?”, “Explain the following terms with one example each. (a) Corrosion (b) Rancidity”, “Oil and Fat containing food items are flushed with Nitrogen. Why?”
Question & Answer
Questions
- ScienceClass 10CBSE
What is hybridization? What are its types, with an example?
Hybridization is the mixing of atomic orbitals in an atom to form new, equivalent orbitals that are better suited for forming chemical bonds. It explains the shape of molecules.Types:TypeOrbitals MixedShapeExample</
- ScienceClass 10CBSE
Explain the following terms with one example each. (a) Corrosion (b) Rancidity
(a) Corrosion is a process where a refined metal is oxidised by atmospheric oxygen to form a more stable compound, such as oxides. The metal gradually degrades during the corrosion process. Rusting of iron is a good example of corrosion where the iron is converted to Iron oxide. Millions of dollars are spent annually in preventing rusting from bridges and other monuments. (b) The condition produced by the aerial oxidation of the oil and fat present in the food material that produces a
- ScienceClass 10CBSE
Oil and Fat containing food items are flushed with Nitrogen. Why?
The main purpose of flushing Nitrogen into food packets that contain oil and fat items is to prevent Rancidity which occurs when the oil or fat reacts with the oxygen letting out an unpleasant smell and taste. Therefore, by flushing Nitrogen, an unreactive surrounding is created, thus preventing rancidity.
- ScienceClass 10CBSE
Why do we apply paint on iron articles?
Iron articles are painted to prevent them from rusting. When left unpainted, the metal surface comes in contact with the atmospheric oxygen and in the presence of moisture it from Iron(III) oxide. But if painted, the surface does not come in contact with moisture and air, thus prevents Rusting.
- ScienceClass 10CBSE
A shiny brown coloured element ‘X’ on heating in the air becomes black in colour. Name the element ‘X’ and the black-coloured compound formed.
The shiny brown-coloured element is Copper metal (Cu). When the metal is heated in air, it reacts with atmospheric oxygen to form copper oxide. Hence, the black-coloured compound is copper oxide. 2Cu(s) + O2(g) → 2CuO(s)
- ScienceClass 10CBSE
Explain the following in terms of the gain of oxygen with two examples each.
(a) Oxidation (b) Reduction Solution: (a) In a chemical reaction, when the oxygen is added to the element to form its respective oxide it is the element being oxidised. Example: 4Na(s) + O2(g) → 2Na2O(s) H2S + O2 → H2O + SO2 (b) In a chemical reaction, when the oxygen is removed from the compound, then it is said to
- ScienceClass 10CBSE
What do you mean by a precipitation reaction? Explain by giving examples.
When two solutions containing soluble salts are combined, a double displacement reaction takes place in which the ions are exchanged between the compounds. When one of such compounds formed is in solid form (that is insoluble in aqua), then it settles down at the bottom of the container. This solid is known as the precipitate and the respective reaction is termed as the precipitation reaction. A few examples of precipitation reactions are CdSO4(aq) + K2S(aq) &rar
- ScienceClass 10CBSE
In the refining of Silver, the recovery of silver from Silver nitrate solution involves displacement reaction by Copper metal. Write down the reaction involved.
Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)
- ScienceClass 10CBSE
What is the difference between displacement and double displacement reactions? Write relevant equations for the above.
A displacement reaction is one when a more reactive substance displaces a less reactive one from its salt solution, whereas a double displacement reaction is one where a mutual exchange of ions happens between two compounds. In a displacement reaction, only a single displacement takes place, whereas in the double displacement reaction, as the name suggests, two displacement takes place between the molecules. Example: Displacement reaction Mg + 2HCl → MgCl<
- ScienceClass 10CBSE
Write one equation each for decomposition reactions in which energy is supplied in the form of heat, light or electricity.
(a) Thermal decomposition reaction (Thermolysis) Decomposition of potassium chlorate: When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. This reaction is used for the preparation of oxygen. 2KClO3 + Heat → 2KCl + 3O2 (b) Electrolytic decomposition reaction (Electrolysis) Decomposition of sodium chloride: On passing electricity through molten sodium chloride, it decomposes into sodium and chlor
- ScienceClass 10CBSE
Why are decomposition reactions called the opposite of Combination reactions? Write equations for decomposition reactions.
Combination reaction is said to be the reaction between two or more molecules to form a larger molecule; whereas the decomposition reaction is defined as the splitting of larger molecules into two or more smaller molecules. This essentially explains that the decomposition reaction is the opposite of the combination reaction. In most cases, the decomposition reaction is endothermic since the heat from the surrounding or induced heat is used to break the bonds of the larger molecule. A
- ScienceClass 10CBSE
What is meant by exothermic and endothermic reactions? Give examples.
An endothermic reaction occurs when energy is absorbed from the surroundings in the form of heat (For example, Photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction is one in which energy is released from the system into the surroundings (Examples: Explosions, concrete setting, nuclear fission and fusion).
- ScienceClass 10CBSE
Write a balanced chemical equation for the following and identify the type of reaction of each case. KBr + BaI2 → KI + BaBr2 ZnCO3 → ZnO + CO2 H2 + Cl → HCl Mg + HCl → MgCl2 + H2
2KBr + BaI2 → 2KI + BaBr2 (Double Displacement Reaction) ZnCO3 → ZnO + CO2 (Decomposition Reaction) H2 + Cl → 2HCl (Combination Reaction) Mg + 2HCl → MgCl2 + H2 (Displacement Reaction)
- ScienceClass 10CBSE
Write the balanced chemical equation for the following reactions. Calcium hydroxide + Carbon dioxide —-> Calcium carbonate + Water Zinc + Silver nitrate —-> Zinc nitrate + Silver Aluminium + Copper chloride —-> Aluminium chloride + Copper Barium chloride + Potassium sulphate —-> Barium sulphate + Potassium chloride
2Ca(OH)2 + 2CO2 → 2CaCO3 + 2H2O Zn + 2AgNO3 → Zn(NO3)2 + 2Ag 2Al + 3CuCl2 → 2AlCl3 + 3Cu BaCl2 + K2SO4 → BaSO4 + 2KCl
- ScienceClass 10CBSE
Balance the following chemical equations. (a) HNO3 + Ca(OH)2 → Ca(NO3)2 + H2O (b) NaOH + H2SO4 → Na2SO4 + H2O (c) NaCl + AgNO3 → AgCl + NaNO3 (d) BaCl2 + H2SO4 → BaSO4 + HCl
(a) 2HNO3 + Ca(OH)2 → Ca(NO3)2 + 2H2O (b) 2NaOH + H2SO4 → Na2SO4 + 2H2O (c) NaCl + AgNO3 → AgCl + NaNO3 (d) BaCl2 + H2SO4 → BaSO4 + 2HCl
- ScienceClass 10CBSE
Translate the following statements into chemical equations and balance them. (a) Hydrogen gas combines with nitrogen to form ammonia. (b) Hydrogen sulphide gas burns in the air to give water and sulphur dioxide. (c) Barium chloride reacts with aluminium sulphate to give Aluminium chloride and a precipitate of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and Hydrogen gas.
(a) Unbalanced: H2 + N2 → NH3 Balanced: 3H2 + N2 → 2NH3 (b) Unbalanced: H2S + O2 → H2O + SO2 Balanced: 2H2S + 3O2 → 2H2O + 2SO2 (c) Unbalanced: BaCl2 + Al2(SO4)3 → AlCl3 + BaSO<s
- ScienceClass 10CBSE
What is a balanced chemical equation? Why should a chemical equation be balanced?
A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equations is necessary for the reaction should obey The Law of Conservation of mass. Balancing the chemical equation has no defined method and is purely a trial-and-error attempt
- ScienceClass 10CBSE
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer. 1. Hydrogen gas and Iron chloride are produced. 2. Chlorine gas and Iron hydroxide are produced. 3. No reaction takes place. 4. Iron salt and water are produced.
Hydrogen gas and Iron chloride are produced. Explanation: The Chlorine from Hydrogen chloride is displaced by the Iron fillings to undergo the following reaction. 2HCl + Fe → FeCl2 + H2
- ScienceClass 10CBSE
Fe2O3 + 2Al → Al2O3 + 2Fe The above reaction is an example of a 1. Combination reaction 2. Double displacement reaction 3. Decomposition reaction 4. Displacement reaction
The answer is 4. Displacement reaction. Explanation: The Oxygen from the Ferrous oxide is getting displaced to the Aluminium metal to form Aluminium Oxide. In this reaction, Aluminum is a more reactive metal than Fe. Therefore, Al will displace Fe from its oxide. This type of chemical reaction, called displacement reaction, is in which one of the elements displaces another. Here, less reactive metal is displaced by more reactive metal. Since one-time displacement is occurring, it is c
- ScienceClass 10CBSE
Which of the statements about the reaction below are incorrect? 2PbO(s) + C(s) → 2Pb(s) + CO2(g) (a) Lead is getting reduced (b) Carbon Dioxide is getting oxidised (c) Carbon is getting oxidised (d) Lead oxide is getting reduced (i) (a) and (b) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all the above
(i) (a) and (b) Explanation: (a) Because Oxygen is being removed and (b) Because the removed oxygen from Lead is added to the elemental Carbon.