Identification of the type of reaction Answer Solutions

Standard 10th Science Experiment 2 Answer Solutions: Identification of the type of reaction Answer Solutions.

Aim : 

To identify the type of reaction.(A) Combustion of magnesium strip in air.(B) Action of dilute sulphuric acid on zinc.(C) Effect of heat on lead nitrate.

Requirements : 

Burner or spirit lamp, matchbox, candle, splinter, hard glass test tube, test tubes, test tubeholder, pair of tongs, beaker, sandpaper, watchglass or china dish, glass rod, candle, etc.

Chemicals : 

Magnesium ribbon, zinc dust, dilute sulphuric acid, lead nitrate powder, blue litmus paper.

( A ) Combustion of magnesium strip in air

Procedure :

1. Take a piece of magnesium strip. Using pair oftongs hold it on the flame of a burner.
2. Collect the remaining ash in watchglass or chinadish. 
3. Identify the type of reaction, record the observationand write the chemical reaction.

Observations :

 (1) The magnesium strip burns with luminous flame. (2) A white coloured powder remains behind.

Inference : 

In this reaction, two reactants combine to form one product. Therefore, this is a

Combinationreaction

. A new substance MgO is formed in the reaction. Hence this change is a chemical change.

Precautions : 

(1) Magnesium strip should be held by a pair of tongs. (2) It is better to use sunglasses to protect your eyes from dazzling light of burning magnesium strip.

(B) Action of dilute sulphuric acid on zinc

Procedure :

(1) Take a big hard glass test tube and fix with clamp stand. (2) Take some zinc dust in a test tube. (3) Add 3 to 4 ml of dilute sulphuric acid in it so that the zinc dust getsimmersed in the acid. (4) Fix a cork having a delivery tube with a fine jet, immediately on themouth of a test tube. (5) Take a lighted candle near the mouth of a fine jet. (6) Record your observations. (7) Identify the type of reaction. Write the chemical reaction.

Observations :

 (1) The reaction is very fast and colourless gas is obtained. (2) The gas burns instantaneously with pop sound. (3) Zinc dust disappears and colourless solution is obtained.

Inferences : 

(1) When atom or group of atoms in one substance takes the place of atom or group of atoms in the othersubstance to form new substances, are called displacement reactions. (2) The hydrogen gas evolved in the reaction. (3) Zn is more reactive than hydrogen. Therefore, the more reactive Zn displaces the less reactive hydrogenfrom sulphuric acid and a colourless solution is obtained.

Precautions :

 (1) Handle acid very carefully. (2) Do not inhale the gas evolved. (3) Hydrogen gas burns with mild explosion, so a fine jet should be used to see the burning of hydrogen.

C) Effect of heat on lead nitrate [Pb(NO3)]

Procedure :

 (1) Take a small amount of lead nitrate white powder in a dry test tube. Hold the test tube with a test tubeholder. (2) Heat the test tube over the flame of the burner. (3) Place the moist strip of the blue litmus paper at the mouth of the test tube. (4) Hold the glowing splinter at the mouth of the test tube. (5) Record your observation. (6) Identify the type of the reaction. Write the chemical reaction.

Inferences : 

(1) When two or more simpler substances are formed from a single compound, the reaction is calleddecomposition reaction. Example : Heating lead nitrate. (2) When lead nitrate is heated Nitrogen dioxide (NO2), Oxygen (O2) are given out and a yellow solid residueof lead oxide (PbO) remains in the test tube. (3) In this reaction, three simple substances are formed from a single compound. Therefore this reaction isa

Decomposition reaction.

 (4) The Nitrogen dioxide gas evolved in this reaction is acidic in nature. Therefore blue litmus turns red.The oxygen gas evolved in this reaction supports burning. Therefore glowing splinter keeps on glowing.

Precaution : 

Do not inhale the gases evolved in this reaction.