Chemistry Past Questions And Answers
An atom23892X decays by alpha particle emission to give an atom Y. The atomic number and mass number of Y are
- A. 90 and 234 respectively
- B. 91 and 238 respectively
- C. 92 and 236 respectively
- D. 93 and 238 respectively
In the discovery of protein, the instrument used is
- A) cathode ray tube
- B) glass tube and discharge tube
- C) discharge tube with terminal cathode
- D) discharge tube with central cathode
Which of the following ions is isoelectronic with neon? [3Li,9F,10Ne,17CI,19K]
- A. CI-
- B. F-
- C. K+
- D. Li+
A sample of temporary hard water can be prepared in the laboratory by?
- A. disolving calcium chloride in distilled water
- B. saturating lime water with carbon (IV) oxide
- C. saturating distilled water with calcium hydroxide
- D. dissolving sodium hydrogen trioxocarbonate (IV) in some distilled water
When anhydrous cobalt chloride paper is exposed to water, what color change is observed?
- A. From pink to blue
- B. From white to blue
- C. From blue to white
- D. From blue to pink
What is the role of iron and aluminium oxide in ammonia production?
- A) dehydrating agent
- B) catalytic agent
- C) oxidizing agent
- D) bonding agent
(a) What is meant by each of the following terms?:
(i) Esterification
(ii) Saponification
(b)(i) Give the general moluecular 1 formula of alkynes
(ii) Write the molecular formula and empirical formula of ethylethanoate.
(iii) Draw the structure of 1, 1, 2, 2-tetrabromoethane
(iv) Write an equation for the reaction of ethanol with sodium
(c) Consider the following reaction schemes:
I II
Petroleum ---> Petroleum Fractions. Higher Petroleum Fractions ---> Petrol + X
(i) State type of process/reaction involved in each of the stages labelled I to IV.
(ii) Identify X and Y
(iii) Give the IUPAC name of the product obtained in stage III.
(iv) What are the reaction conditions for stage IV?
(d) Explain why palm wine: (i) froths or foams (ii) tastes sour after some days.
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The cleansing effect of soap is low in acidic water because of
- A. the formation of unionized fatty acid.
- B. increase in the pH of the soap molecules.
- C. anti-biodegradable effect of hydrogen ions
- D. the hardness of the acidic water.
Alkanals can be differentiated from alkanones by reaction with
- A) 2, 4 - dinitrophenylhydrazine
- B) hydrogen cyanide
- C) sodium hydrogen sulphite
- D) Tollens' reagent
Which of the following statements is/are correct about tin plating? l The electrolyte must be a soluble salt of tin ll. the objective to be plated is made the cathode lll. The anode is made of tin lV. The negative electrode dissolves
- A. L only
- B. l and ll only
- C. l,ll and lll only
- D. l, ll and lV only