20 CHEMISTRY QUESTIONS WITH ANSWERS 100 LEVEL STUDENTS SHOULD STUDY

1. Which of the following reagents would be most suitable for reducing 2-bromo-2-methyl propane to      2-methyl propene? (a) Zn/CH3COOH (B) NaBH4 (C) LiAlH4 (D) Alcoholic KOH.

Ans- D. (Alcoholic KOH) Explanation: The reduction of 2-bromo-2-methyl propane to 2-methyl propene is known as dehydrohalogenation reaction (that is removal of hydrogen and halogen). This reaction takes place in the presence of a strong base, and it is used to produce alkenes. 

 2. The acid obtained from crushed ants is ________________

Ans- Methanoic acid or formic acid (that is the first member of the carboxylic group [HCOOH]) 

 3. ----O----; this functional group represents_________________

Ans- Ether

4. CH3-CH=CH2 + HCL A, A is _______________

Ans- A is 2-chloro propane. This reaction is known as addition reaction (that is addition of unsymmetrical reagents) using the markwonokoff’s rule. 

 5. What is the monomer unit of polyvinyl chloride?

Ans-Vinyl chloride (-CH2CH2CL)

 6. (CH3)2C=CHCH3 + O3 →F →A + B ; F, A and B are ___________, __________ and ______________. this reaction is taking place in the presence of zinc in dilute acid.

Ans-F is an ozone, A  is propanone while B is ethanal 

7. What is the colour of bromine in CCL4 when 2-butene is added?

Ans-colourless. This reaction is used as a test for alkenes. 

8. What is the reagent used to convert propyl chloride to propene?

Ans-Alcoholic KOH is used. The reaction is known as dehydrohalogenation reaction which requires a strong base (same as number 1) 

9. List four methods used to prepare alkenes.

Ans-(a) dehydration of alcohols using conc. H2SO4 in the presence of heat. 
        (b) Dehydrohalogenation reaction using a strong base. 
        (c) Dehydrogenation reaction of alkanes in the presence of catalyst. 
        (d) Dehydrogenation of 1, 2-dihalide 

10. CH3C CCH3 + H2 (lindlar catalyst)    →A.

Ans-A is cis-but-2-ene(CH3CH=CHCH3). Therefore reacting but-2-yne with lindlar catalyst gives a cis-but-2-ene. 

11. Two reagents used in the identification of terminal alkynes are ____________and _____________

Ans-Silver nitrate in ammonia solution (Ag[NH3]2²⁺). This gives a white precipitate with terminal alkynes. 

Ammonical solution of copper(1) chloride (cu[NH3]2⁺). This gives a red precipitate with terminal alkynes. 

12. With which reagents does propyne gives a completely different reaction from propene?

Ans-Ammonical solution of copper(1) chloride (cu[NH3]2⁺). This reagents gives a positive test only with alkynes. 

13. Which reagents will react with an alkene to form a trans diol?_____________

Ans- Hydrogen peroxide 


14. Which of the following is correct about inductive effect? (a) Increase with bond angle (b) has lower bond energy. (c) Dies away with increase in distance. (d) Is an effect of unsaturated compounds

Ans- C. Dies away with increase in distance. Reason: inductive effect is the shifting of electrons in a nuclei due to the presence of a nearby electronegative element. Using the molecule below:                                   
                              3      2      1        
                              CH3CH2CH2CL 
                                                           
Since chlorine is a very electronegative element than carbon, it will draw the electrons present in the nuclei of chlorine and C-1 closer to itself, C-1 will also exhibit this effect (that is by withdrawing electrons from C-2) but in a minimum amount. Therefore, as you move away from chlorine the effect reduces. 

15. Exterification of propane-1,2,3-triol and unsaturated higher carboxylic acid will produce_________ (a) Fat (b) soap (c) methyl-propanoate (d) alkanols (e) oils.


Ans- Exterification reaction leads to the formation of esters (Alkanoate). Therefore (option C) is correct since methyl-propanoate is an ester. 

16. When starch undergoes complete enzyme-catalyzed hydrolysis, the resulting product is _________ (a) Glucose (b) maltose (c) sucrose (d) fructose (e) cellulose.

Ans-Maltose (option B). 

17. Which of the following is suitable for determining different isotopes present in an element which exhibit isotopy? (a) Geiger Muller counter (b) sensitive weighing balance (c) mass spectrometer (d) cathode ray tube (e) eudiometer.

Ans- mass spectrometer is a device that is majorly used to detect the mass of an element. This device displays different peaks with different mass value (this peaks shows the different mass of the atom fragment). [option C] 

 18. (a) Explain what is meant by effective collision? (b) What deduction can be made about a system in which its G is zero?

Ans- (a) effective collision is a collision in which the reacting molecules must be properly oriented and also the reacting molecules must collide with enough energy for bond to break (activation energy).

(b) When G is zero it means that the reaction system is at equilibrium (that is the rate of formation of product is equal to the rate of formation of reactants). 

 19. Suggest three conditions necessary for maximum yield of A2B in the reaction represented by the following equation:                            

                                                 2A2 + B2 →2A2B        ∆H= xkj


Ans- Observing the equation below carefully, we can see that H is positive (that is the reaction is endothermic). The following conditions will give maximum yield of A2B:
 • Increase in temperature 
• Decrease in pressure and, 
• Increase in concentration. To have more understanding about exothermic and endothermic reaction click here

20. It has been observed that hydrogen peroxide decomposes when expose to air. Which regents can be used to slow down the decomposition? _________

Ans- mineral avid like: HCL, H2SO4, H3PO4 which serve as a negative catalyst by reducing the rate of the reaction can be used. 

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