Chemistry Questions and Answers - Form 1 Mid Term 2 2022

QUESTIONS

1.      
   1. What are acid – base indicators. (1mk)
   2. Solutions are classified as strongly basic, weakly basic, neutral, weakly acidic or strongly acidic. The information below gives solutions and their pH values. Study it and answer the questions that follow.
      

      Solution	pH values	Classifications
      U V W X	14 6 9 2

      Which of the solution could be?
      
      1. Dilute nitric (v) acid. (1mk)
      2. Wood ash extract. (1mk)
      3. Sodium Hydroxide. (1mk)
      4. Rain water in an industrial polluted region. (1mk)
      5. What is the name given when solution U react with solution X. (1mk)
   3. State three examples of acid-base indicators and state the colors they show in acid and basic solutions. (4 ½ mks)
      

      Indicator	Color of indicator in
      	Acid	Base
      i) ii) iii)

   4. State the advantage of universal indicator over other acid-base indicator. ( ½ mk)     
2.  
   1. State the effects of adding impurity to the melting and boiling points of water. (1mk)
   2. State one application of adding impurities on substances. (1mk)
   3. Write the chemicals symbols of the following elements and their Latin names. (5mks)
      

      Element	Latin name	Symbol
      i) Potassium ii) Silver iii) Iron iv) Copper v) Mercury

3.    
   1. Copper (II) oxide was contaminated with iodine crystals. Describe how iodine can be obtained from the mixture. (2mks)
   2. Below is a heating curve for ice until it formed steam. Use it to answer the questions.
      
      On the same axis, plot the curve that would be obtained if ice was contaminated with Sodium Chloride. (1mk)
4.    
   1. State 4 differences between luminous and non-luminous flame. (4mks)
      

      Luminous	Non-luminous
      i) ii) iii) iv)

   2. List two laboratory rules. (2mks)
   3. Chromatograph below represents the results of an experiment done with certain plant pigments. Study it and answer a question that follows.
      
      
      1. Name the part labeled X. (1mk)
      2. Which two pigments is the component of P. (1mk)
      3. Which of the pigments x, y and z is the least soluble? (1mk)

MARKING SCHEME

1.    
   1. A substance that gives a specific color in an acid and another specific color in a base.√
   2. 
      

      Solution	pH values	Classifications
      U V W X	14 6 9 2	Sodium hydroxide√ Rain water√ Wood ash extract√ Dilute Nitric(v) acid√

      Which of the solution could be;
      i) Dilute nitric (v) acid. (1mk)
      ii) Wood ash extract. (1mk)
      iii) Sodium Hydroxide. (1mk)
      iv) Rain water in an industrial polluted region. (1mk)
      v) What is the name given when solution U react with solution X. (1mk)
      Neutralization.
   3. Indicator Color of indicator in
      

      Indicator	Color of indicator in
      	Acid	Base
      i)Methyl orange √ ii)Litmus solution√ iii)Phenolphthalein√	Pink/red √ Red√ Colourles√	Yellow√ Blue√ Pink √

   4. It gives strength of acid or base. √ ( ½ mk)
2.        
   1. m.p lowered √
      b.p raised√
   2. Extraction of metals from their ores.
      Melting of ice on roads during winter.
   3. 
      

      Element	Latin name	Symbol
      i) Potassium ii) Silver iii) Iron iv) Copper v) Mercury	Kalium√ Argentums√ Ferrum √ Cugrum√ Hydragylum√	K√ Ag√ Fe√ Cu√ Hg√

3.      
   1. Heat the mixture iodine sublimes and settles on cover parts√ scoop it with spatula.√
   2.       
      
4.      
   1. 
      

      Luminous	Non-luminous
      i) Sooty flame√ ii) Wavy flame√ iii) Bright yellow flame √ iv) Has 4 religions burns quietly √	Non sooty flame √ Steady flame √ Blue less bright flame √ Have 3 regions burns with rolling sound.

   2. List two laboratory rules. (2mks)
      
      • Never taste anything in lab.
      • Do not smell gas directly.
        N/B any correct rule.√
   3.      
      1. Baseline // origin√
      2. Y and Z√
      3. x√