Lecture 4 : Revision

Write the balanced equation for the following chemical reactions.

(i) Hydrogen + Chlorine → Hydrogen chloride

(ii) Barium chloride + Aluminium sulphate → Barium sulphate +

Aluminium chloride

(iii) Sodium + Water → Sodium hydroxide + Hydrogen

State the type of chemical reactions with chemical equations that take place in the following.

(i)   Magnesium wire is burnt in air.

(ii)   Electric current is passed through water.

(iii)  Ammonia and hydrogen chloride gases are mixed

(i) Identify the type of reactions taking place in each of the following cases and write the balanced chemical equations for the reactions.

    (a) Barium Chloride solution is mix with copper sulphate solution and a white precipipate is              obtain.

     (b) On heating copper powder in air, the surface of the copper powder turns black.

(ii) What happens when hydrogen gas is passed over the heated copper oxide? Write the chemical equation involved in this reaction.

State one example each characterised by the following along with the chemical equation:

(i) Change in state

(ii) Evolution of gas

(iii) Change in temperature

Which of the statements about the reaction below are incorrect?

(a) Lead is getting reduced.

(b) Carbon dioxide is getting oxidised.

(c) Carbon is getting oxidised.

(d) Lead oxide is getting reduced.

(i) (a) and (b)

(ii) (a) and (c)

(iii) (a), (b) and (c)

(iv) all

Give one example of a combination reaction in which an element combines with a compound to give you a new compound.

Ahmad took a magnesium ribbon (cleaned) and burned it on a flame. The white powder formed was taken in a test tube and water was added to it. He then tested the so lution formed with red and blue litmus paper. What change was seen? Why?

A water insoluble substance ‗X‘  on reacting with dilute H2SO4  released a colourless and odourless gas accompanied by brisk effervescence. When the gas was passed through water,the solution obtained turned blue litmus red. On bubbling the gas through lime water, it initially  became  milky  and  milkyness  disappeared  when  the  gas  was  passed  in  excess.Identify the substance ‗X‘. Write its chemical equations of the reactions involved.

Does hydrogen gas support combustion?

Name one metal which does not corroded?

What “aq” stands for?

What do you mean by Rancidity?

The substance oxidized in a redox reaction is called……………………… agent.

Why Hydrogen Peroxide kept in colored bottles?

What is an oxidizing agent?

Can we place silver nitrates solution in an iron vessel? Why or Why not?

Suggest two methods to prevent rancidity?

In the following reaction:

MnO₂ + 4HCl→ MnCl₂ +2H₂O+Cl₂

       a) Name the substance oxidized.                                                                                    

       b) Name the substance reduced.

(a) Why can not a Chemical change be normally reserved?

        (b) Why it is always essential to balance a chemical equation?

        (c) Can rusting of iron take place in distilled water?

        (d) How will you know whether a sample of cheese has become rancid or not?

Identify the type of reaction in the following?

       (a) ZnCO₃ (s) + 2HCl (aq) → ZnCl₂(aq) +H₂CO₃ (aq)

       (b) 2NaBr (aq) + Cl₂ (g) → 2NaCl (aq) + Br₂ (aq)

       (c) 2CuO (s) → 2Cu (s) +O₂ (g)

       (d) 2Na (s) + Cl₂ (g) → 2NaCl (s)

(a) Why is combustion reaction an oxidation reaction?

(b) How will you test whether the evolved in a reaction is hydrogen?

        (c) Why does silver not evolve hydrogen gas on reacting with dilute sulphuricacid

How can a balanced equation be made more informative? Explain with example?

On what basic Reaction is black and white photography based?

Name the substance Oxidized and Reduced in the Chemical Reaction

MnO₂ + 4HCl → MnCl₂ +Cl₂ +2H₂O

Solid calcium Oxide was taken in a container and water was added slowly to it

i. State two observation made in the experiment.

        ii. Write the name of the chemical formula of the product.

Why do potato chips manufacturers fill the packets with nitrogen gas?

The gases H₂ and Cl₂ do not react with each other even if kept together for a long time however in the presence of sunlight, they readily combine. What does actually happen?

When Carbon dioxide is passed through lime water, first it turns milky and on further passing the gas milkiness disappear explain why?

Why a few drops of sulphuric acid are added into water before electrolysis?

When Lead Nitrate combines with Potassium Iodide a yellow precipitate forms

What Chemical compounds is used in white wash of walls? What happens when we mix it with water? What reaction takes place on the walls after thewhite wash?

Astha has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings Test Tube CuSO4 Solution Iron Nail

Thread

A student dropped few pieces of marble in dilute HCl contained in a test tube. The gas evolved was passed through lime water. What change would be observed in lime water? Write chemical reactions for both the changes observed. 

A student burnt a metal A found in the form of ribbon. The ribbon burnt with a dazzling flame & a white powder B is formed which is basic in nature. Identify A & B.Write the balanced chemical equation.

A reddish brown metal X when heated in presence of oxygen forms a black compound Y which is basic in nature when heated with hydrogen gas gives back X. Identify X & Y.Write the chemical reaction between Y & H 2 Identify the substance being oxidized & reduced.

A student has mixed the solutions of lead (II) nitrate and potassium iodide.

(i) What was the colour of the precipitate formed? Can you name the compound?

precipitated ?

(ii) Write the balanced chemical equation for this reaction.

(iii) What type of reaction is it?

A substance X used for coating iron articles is added to a blue solution of areddish brown metal Y,the color of the solution gets discharged Identify X and Y & also the type of reaction.

A reddish brown vessel developed a green colored solid X when left open in air for a long time. When reacted with dil H2SO4 , it forms a blue colored solutionalong with brisk effervescence due to colourless & odourless gas Z. X decomposes to form black colored oxide Y of a reddish brown metal along with

gas Z, Identify X, Y, & Z. 

A student took 2-3 g of a substance X in a glass beaker & poured water over it slowly. He observed bubbles along with hissing noise. The beaker becomes quite hot. Identify X.What type of reaction is it?

Bhawana took a pale green substance A in a test tube. and heated it over the flame of a burner. A brown colored residue B was formed along with evolution of two gases with burning smell of sulphur.Idetify A & B. Write the chemical reaction involved.

An aqueous solution of metal nitrate P reacts with sodium bromide solution to form yellow ppt of compound Q which is used in photography. Q on exposure to sunlight undergoes decomposition reaction to form metal present in P along with reddish brown gas. Identify P&Q . Write the chemical reaction & type of chemical reaction.

A compound `X` is used for drinking, has pH =7.Its acidified solution undergoes decomposition in presence of electricity to produce gases `Y` and `Z` The volume of Y is double than Z. Y is highly combustible whereas Z is supporter of combustion .Identify X, Y & Z and write the chemical reactions involved.

Explain the following terms with one example each.

(a) Corrosion

(b) Rancidity

Oil and fat containing food items are flushed with nitrogen. Why?

Why do we apply paint on iron articles?

 A shiny brown-coloured element "x"on heating in air became black in colour.Name the different element"x"and the black coloured compound formed.

Explain the following in terms of gain or loss of oxygen with two examples each.

(a) Oxidation

(b) Reduction

  What do you mean by a precipitation reaction? Explain by giving examples.

  In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal.Write down the involved reaction.

What is the difference between displacement and double displacement reactions? Write equations for these reactions.

Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

 Why are decomposition reactions called the opposite of combination reactions?

Why is respiration considered an exothermic reaction? Explain.

What does one mean by exothermic and endothermic reactions? Give examples.

 Write the balanced chemical equation for the following and identify the type of reaction in each case.

(a)Potassium bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) +Barium bromide(s)

(b) Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g)

(c) Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)

(d) Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g)

Write the balanced chemical equations for the following reactions.

(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

(b) Zinc + Silver nitrate → Zinc nitrate + Silver

(c) Aluminium + Copper chloride → Aluminium chloride + Copper

(d) Barium chloride + Potassium sulphate → Barium sulphate +

Potassium chloride

Balance the following chemical equations.

(a) 

(b) 

(c) 

(d) 

Translate the following statements into chemical equations and then balance them.

(a) Hydrogen gas combines with nitrogen to form ammonia.

(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

What is a balanced chemical equation? Why should chemical equations be balanced?

What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer.

(a) Hydrogen gas and iron chloride are produced.

(b) Chlorine gas and iron hydroxide are produced.

(c) No reaction takes place.

(d) Iron salt and water are produced

The above reaction is an example of a

(a) combination reaction.

(b) double displacement reaction.

(c) decomposition reaction.

(d) displacement reaction.

Identify the substances that are oxidised and the substances that are reduced in the following reactions.

(i)

(ii) 

Give an example of a double displacement reaction other than the one given in Activity 1.10.

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.

A solution of a substance ‘X’ is used for white washing.

(i) Name the substance ‘X’ and write its formula.

(ii) Write the reaction of the substance ‘X’ named in (i) above with water.

Write a balanced chemical equation with state symbols for the following reactions.

(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Why should a magnesium ribbon be cleaned before it is burnt in air?