A. Answer the following questions in about twenty words.
1. Write a word equation for a reaction in which sodium carbonate reacts with hydrochloric acid ?
2. Define a chemical reaction.
3. Mention the characteristics of chemical reactions.
4. Give one reaction which is characterised by a change in colour.
5. Mention the reaction that take place during white washing.
Answers
Answer:
1.When solutions of sodium carbonate and hydrochloric acid are mixed, the equation for the hypothetical double displacement reaction is: Na2CO3 + 2 HCl → 2 NaCl + H2CO3 Bubbles of a colorless gas are evolved when these solutions are mixed.
2.A chemical reaction is a process in which one or more substances, also called reactants, are converted to one or more different substances, known as products. ... Chemical reactions differ from physical changes, which include changes of state, such as ice melting to water and water evaporating to vapor.
3.The characteristics of a chemical reaction are: Evolution of gas, Formation of a precipitate, Change in colour, Change in temperature, Change in state etc.
4.Change in colour : The reaction between lead nitrate solution and poassium iodide solution. In above reaction colour change from colourless to yellow.
5.i don no
Explanation:
Answer:
1. Na2CO3 + 2 HCl → 2 NaCl + H2CO3
2. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.
3. The characteristics of a chemical reaction are: Evolution of gas, Formation of a precipitate, Change in colour, Change in temperature, Change in state etc.
4. The reaction between lead nitrate solution and poassium iodide solution. In above reaction colour change from colourless to yellow.
5. Quicklime is used for whitewashing as it produces calcium hydroxide (CaOH) when it reacts with water (H2O) and absorbs carbon dioxide (CO2) from the environment, as a result, it produces calcium carbonate (CaCO3) which creates a hard coating on the walls. CaO (s) + H2O (l) → Ca(OH)2(aq).