Chemical Reactions And Equations Class 10 Questions- Practice
Q.1. A water insoluble substance ‘X’ on reacting with dilute H2SO4 released a colourless and odourless gas accompanied by brisk effervescence. When the gas was passed through water, the solution obtained turned blue litmus red. On bubbling the gas through lime water, it initially became milky and milkyness disappeared when the gas was passed in excess. Identify the substance ‘X’. Write its chemical equations of the reactions involved.
Answer-The water insoluble substance ‘X’ is metal carbonate CaCO3.
CaCO3 (S) + H2SO4 (Aq) → CaSO4(Aq) + H2O (Aq) + O2 (G)
Ca(OH)2 + CO2 (G) → CaCO3 (S)(milky) + H2O (L)
CaCO3 (S) + CO2 (G)+ H2O (Aq) → Ca(OH)2 (milkiness)
Q.2. Ahmad took a magnesium ribbon (cleaned) and burned it on a flame. The white powder formed was taken in a test tube and water was added to it. He then tested the solution formed with red and blue litmus paper. What change was seen? Why?
Answer- Red litmus paper turned blue.
Blue litmus paper remained blue.
This is because the magnesium ribbon on burning in air forms the white magnesium oxide. Which dissolved in water, it forms magnesium hydroxide, which is Basic in nature.
Q.3. Give one example of a combination reaction in which an element combines with a compound to give you a new compound.
Answer-O2 + 2SO2 → 2SO3
8NH3 + 3Cl2 → 6NH4Cl
Solve Chemical Reactions And Equations Class 10 Questions
Q.4. Marble statues often slowly get corroded when kept in open for a long time. Assign a suitable explanation.
Q.5. Mohan took pure water for the electrolytic decomposition of water but did not see any bubbles near the electrodes. Explain why?
Q.6. Rancidity is a process used for spoiling of cooked food materials like vegetables, etc. When kept for long time in open. How can you prevent such process to proceed? Give an example.
Q.7. A substance ‘X’ displaces ‘Y’ from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain, giving an example?
Q.8. A grey coloured metal ‘Z’ (Atomic weight=65) is used in making dry cell. It reacts with dil. HCl to liberate a gas. What is the gas evolved? Calculate the minimum amount of ‘Z’ required to produce 100 litres of gas?
Q.9. Why is respiration considered an exothermic reaction? Explain.
Q. 10. Why are decomposition reactions called opposite of combination reactions? Write equations for these reactions.
Q.11. A shiny brown colored element ‘X’ on heating in air becomes a black coloured compound. Name the element ‘X’& black the coloured compound formed. Also write the equation
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