Central Board of Secondary Education (CBSE)
Sample Paper – 2012
Class – X
Subject – Chemistry
- What will be when magnesium ribbon burns in air?
- Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
- Write the conditions, when do you say that a chemical reaction has taken place?
- What do you mean by chemicalequation?
- Why decompotion reactions are called the opposite of combination reactions?
- What are redox reactions? Give examples.
- Why do we balance a chemical equation?
- What is hit and trial method of balancing chemical equation?
- What does the word “aq” represent in a chemical equation?
- What actually happen during a chemical reaction?
- Why water starts boiling if lime is added to it.
- The glucose combines with oxygen in our body cells and provides energy. What is the special name of this reaction?
- Is lime natural or man-made substance? Why? , Give one use of it.
- Why during electrolysis of water some drops of sulphuric acid is added.
- In what ratio of hydrogen and oxygen formed during electrolysis of water and why?
- Why silver chloride does is stored in dark coloured bottles.
- What do you mean by recipitates?
- A reddish brown element X on heating converted into a black coloured compound Y. Give interconversion reaction of X and Y.
- What is rancidity? Mention four methods to slow down it.
- What does a complete chemical reaction represent?
- What do you mean by oxidation-reduction reaction. Give an example to explain this.
- Write the definition of antioxidants?
23. What happens when: Write the chemical balance equation
a. Hydrogen gas combines with nitrogen to form ammonia.
b. Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
c. Barium chloride reacts with aluminum sulphate to give aluminum chloride and a precipitate of barium sulphate.
d. Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
24. Write balanced chemical equation for all the above.
a. BaCl2 + H2SO4à BaSO4 + HCl
b. NaCl + AgNO3àAgCl + NaNO3
c. NaOH + H2SO4à Na2SO4 + H20
d. HNO3 + Ca(OH)2àCa(NO3)2 + H20
25. Why do we use AgNO3 in black and white photography.
Sample Paper / Model Test Paper CBSE 12th 2012