CBSE Pathshala

Q. How is NH4OH used as a laboratory reagent? Answer:  NH4OH is used to detect cations in their salt solutions by precipitating their hydroxides whose colour and solubility in excess NH4OH, identifies them. Q. Though NaHSO 4  solution releases H +  ions, why is it not called an acid? Answer:  NaHSO 4  solution is not called an acid because an acid should release only H +  ions as positive ions and not any other positive ions. But NaHSO 4  is solution releases H +  ions as well as Na +  ions also as positive ion. Q. How would you distinguish between baking powder and washing soda by heating? Answer: Sodium hydrogencarbonate on heating gives CO2 gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate. 2NaHCO3 ---Heat → Na2CO3 + H2O + CO2      Na2CO3.10H2O -Heat → Na2CO3 + 10H2O Q. Why aqueous solution of sodium carbonate is basic in nature? Answer: Sodium bicarbonate...

ASSIGNMENT : FIRST TERM (2012-2013)  X - CHEMISTRY                          CHAPTER: ACIDS AND BASES                       Max Marks: 25 A. Very short answer questions: (1 mark each) (1x 6= 6marks) 1. A calcium compound which is yellowish white powder is used as a disinfectant and also in textile industry. Name the compound. Which gas is released when this compound is left exposed to air ? 2. Which element is common to all acids ? 3. What is common name of water soluble bases ? 4. Write the neutralization reaction between acids and bases in terms of the ions involved. 5. Two solutions A and B have pH values 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink....