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Lesson (3) Chemical Equations and Reactions
I. Choose the correct answers:
1. The bright magnesium ribbon changes into white powder of ------ when it burns in air.
(magnesium nitrite – magnesium hydroxide – magnesium dioxide –
magnesium oxide )
2. Ammonia combines with HCl producing -------- of ammonium
chloride
(white ppt – brown fumes – white fumes – brown ppt)
II. Give reasons for:
1. A chemical equation should be balanced.
To achieve the low of conservation of matter .
2. A white cloud is formed when ammonia gas reacts with conc.
hydrochloric acid.
Because the ammonium chloride is formed .
NH3+HCL
CONC
NH4CL
3. A white powder is formed when a magnesium strip burns in
air .
Because the magnesium oxide is formed
2Mg+O2
2MgO
4. Chemical reactions have useful and harmful effects.
Look at your school book page 31 and32
5. CO2 gas acts as greenhouse effect.
Because it permits the penetration of thermal rays from
the sun to the earth and neverlet them return back.
6. Burning of coal and cellulose fibers has bad effect.
Because it causes air pollution and lung cancer.
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7. Carbon monoxide is a dangerous gas.
Because it causes headache,fainting in addition to severe
stomach aches and may lead to death.
III. write the chemical equation representing the following
reactions, then indicate the type of the reaction :
1. Heating magnesium ribbon in air.
2Mg+O2
2MgO
Direct combination reaction ( element with another
element)
2. Burning of carbon in the presence of oxygen.
C+O2
CO2
Direct combination reaction ( element with another
element)
3. Reaction of ammonia gas and hydrochloric acid.
4. NH3+HCL
CONC
NH4CL
Direct combination reaction ( compound with another
compound )
IV. What happens in each of the following : [explain your
answer with balanced symbolic chemical equations if it is
possible].
1. Burning a magnesium ribbon in air.
White powder of magnesium oxide is formed
2Mg+O2
2MgO
2. Putting a glass rod wet with ammonia solution close to the
opening of a test tube containing conc. hydrochloric acid.
White fumes of ammonium chloride is formed
1. NH3+HCL
CONC
NH4CL
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V. Write the scientific term for each of the following:
1. It's the process in which bonds in reactants are broken and
bonds in resultants are formed…chemical reaction ……………
2. It's a set of symbols and chemical formula representing the
reactants and the products molecules in the chemical reaction
and the conditions of the reaction…chemical equation …………
3. The total amount of reactants masses is equal to the total
amount of products masses ………low of conservation of matter
or mass………………
VI. The following questions are related to the following
equation
2Mg + O2
2MgO
1. The reactants are …………Mg…. & …………O2………
2. The product is …MgO……………………
3. The breaking of the bond in the oxygen molecule gives 2
active oxygen ………atoms ………………
VII. Complete the following equations:
1- C + O2
………CO2……
2- 2NO + ……O2……….
2 NO2
4-NH3+HCl
………NH4CL…………..
VIII.Mention the harmful effect of the following:
1. Carbon monoxide
2. Nitrogen oxides
3. Sulphur oxides
LOOK AT PAGE 31 AND 32
4. Carbon dioxide
5. Burning of cellulose fibers.
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