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Subject:

science-chemistry

Class:

class VIII

Key Concepts

acids, bases, indicator, neutralization, salt, basic, acidic, reactions

essential questions

1.What are acids and bases?
2 What are some properties of acids and bases?
3 What is pH and how does it measure the concentration of acids and
bases?
4 How do acids and bases react with each other?

Remembering:

  1. Which one is correctly matched?  a)Acids – pH range above7    b) Acids – pH range below 7
    c) Acids – pH range 7( neutral)    d) Acids – pH range 8-9
  2. A strong acid is same as concentrated acid. State true or false
  3. When an acid reacts with a metal, which one of the following gas is usually liberated?  a) ammonia gas    b) chlorine   c) oxygen    d) Hydrogen gas
  4. Select the one which is wrongly mapped: a)Sodium carbonate – Washing soda   b) Sodium chloride – common salt    c) Calcium carbonate – slaked lime   d) Sodium hydroxide – caustic soda
  5. Which type of solution is one with a pH of 8: a) acidic   b) basic   c) neutral
  6. You should never taste or touch to identify a base because they can be: a) Corrosive  b) Slippery  c) Sour  d) Antacids
  7. One of the physical properties that all acids have is: a) no color  b) color  c) sour taste  d) bitter taste
  8. Which ion do bases contain: a) OH-  b) H3O   c) H+  d) NH4
  9. Acids make litmus paper turn : a) red  b) blue  c) yellow  d) black
  10. Bases feel : a) rough  b) slippery  c) moist  d) dry
  11. Acids taste: a)sweet   b)bitter  c)salty  d)sour
  12. Calamine solution contains: a) Zinc hydroxide   b) Zinc carbonate   c) Sodium hydrogen carbonate  d) Magnesium hydroxide
  13. pH of the human body varies within the range of : a) 6 to 6.5   b) 5.5  to 5.8   c) 7.0  to 7.8  d) 7.0 to 11.0
  14. Acid rain is casued due to ____ a) CO2, O2, SO2   b) CO2, NO2, H2   c) SO2, N2, O2   d) CO2, SO2, NO2
  15. Acids are ____in taste while bases are ___ in taste.
  16. The presence of which of the following acids cause indigestion. a) citric acid   b) oxalic acid  c) acetic acid   d) hydrochloric acid
  17. Baking powder is a) mixture b) compound  c) element  d) salt
  18. Dead burnt plaster: a) quick lime  b)  slaked lime  c) limestone  d) gypsum
  19. Which of the following pairs of substance are chemically same: a) Lime water  and milk of lime   b) Dead burnt plaster and gypsum  c) both of the above  d) none of the above
  20. Plaster of Paris is obtained by: a) adding water to calcium sulphate   b) by adding sulphuric acid to calcium hydroxide  c) by heating gypsum to a very high temperature  d) By heating gypsum to 373K
  21. Which is not a typical property of acids:  a) they react with water producing alkalis with water  b)They react with all metals producing hydrogen   c) they react with carbonates producing CO2    d) They turn litmus paper red
  22. Which of the following are acidic and basic in nature: Vinegar, limewater, stomach juices, milk of magnesia, baking soda

understanding:

  1. Weak acids don’t ionize to a high degree in water, so they produce few: a) electrolytes  b) hydrogen ions  c) hydroxide ions  d) carbonates
  2. Which type of reaction always forms a salt and water: a) exothermic  b) neutralization  c) oxidation  d) polymerization
  3. Bases react with : a) acids to produce salts and water  b) water to produce acids and salts  c) salts to produce acids and water  d) neither acids, salts nor water
  4. A compound is a salt if it:  a) can neutralize an acid  b) contains more than one element  c) dissolves in water d) is formed when an acid reacts with a base
  5. Which of the following is a strong base: a) NaCl    b) H2CO3  c) HCl  d) Ca(OH)2
  6. Aqueous solution of which of the following salt will change the colour of red litmus to blue: a) Na2 CO3   b) Na2 CO3.10H2O  c) Both a and b   d) none
  7. Reaction of metal with acid results in the formation of a) only hydrogen gas  b) only salt  c) both salt and hydrogen gas  d) none

Other Questions:

  1. What are acids and bases? Explain with equation.
  2. Write 4 differences between acids and bases.
  3. What are the various ways in which acids are prepared? Give equations for each method.
  4. Why does a turmeric stain on white shirt is turned to red when it is washed with soap
  5. Fill in the blanks:

a)Effect of an wasp sting can be neutralized by vinegar because its _______ in nature ( acidic / alkaline)

b)Effect of a bee sting can be neutralized by bicarbonate of soda because its ______ in nature ( acidic/ alkaline)

c) Fruits are _____ in nature ( acidic / base)

d) Reaction between acids and base is called as _______ ( neutralization/ displacement)

e) Correct way of making acid using water is to _______ (pour acid in water / pour water in acid)

 

Application:

  1. MgO + 2HCl —-> X + H2O
    a) Mg2Cl    b) 2MgCl     c) MgCl   d) MgCl2
  2. Select the one which is neither an acid nor base
    a) CH3COOH    b) HCl     c) KCl    d) CH3OH
  3. Which one will change from red litmus to blue: a) NaCl    b) HCl    c) KOH  d) LiOH
  4. A solution with a pH of 1 is a: a) Strong acid   b) Buffer   c) Weak acid   d) Strong base
  5. To protect tooth decay we are advised to brush our teeth regularly. The nature of the tooth paste commonly used: a) acidic   b) neutral  c) basic  d) corrosive
  6. Common salt besides being used in kitchen can also be used as the raw material for making i) washing soda  ii) bleaching powder  iii) baking soda  iv) slaked lime    a) i and ii  b) i, ii and iv   c) i and ii   d) i, iii and iv
  7. Why bases are kept in glass bottles: a) bases produce OH∼ions in aqueous solution   b) Basic solution are conducive in nature  c) bases are corrosive in nature  d) Basis have soapy texture
  8. When vinegar reacts with baking soda the gas evolved is : a) hydrogen  b) oxygen  c) carbon di oxide  d) nitrogen dioxide
  9. If pH of A, B, C, D are 9.5, 2.5,3.5 and 5.5 respectively, the strongest acid is: a) A   b) B  c) C  d) D
  10. When the stopper of a bottle containing liquid was removed, the bottle gave smell like that of vinegar. The liquid in the bottle could be  a) Hydrochloric acid   b) Sodium hydroxide solution  c) acetic acid solution  d) saturated sodium hydrogen carbonate solution
  11. Which of the following is acidic in nature: a) apple juice  b) soap solution  c) slaked lime  d) lime

Other Questions

  1. After a neutralization reaction, why does the test tube turn hot?
  2. The soil of a farm land is producing low yield. Can you think of reasons why the crop yield has gone low and what steps should be taken to improve it.

Analysis:

  1. When a few drops of lemon are mixed with milk 1) it turns sour   ii) no change takes place  iii) properties of milk change  iv) properties of milk remain same.  a) ii and iii    b) i and ii  c) i and iii

Evaluation:

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