Before we go further and study the types of chemica
Very Short Answer Type Questions
1. Why is respiration considered an exothermic proce
2. On what basis is a chemical equation balanced ?
3. What happens chemically when quicklime is adde
4. Why should magnesium ribbon be cleaned before
5. State whether the following statement is true or fa
A chemical equation can be balanced easily by alte
6. What is wrong with the following chemical equati
Mg
+ O
→ Mgo
Correct and balance it.
7. What does the symbol (aq) represent in a chemica
8. Wh
Answers
Answer:
Textbook Solutions Class 10 Science Chemical Reactions And Equations
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Page No 18:
Question 1:
Why is respiration considered an exothermic process?
ANSWER:
In respiration, glucose undergoes slow combustion by combining with oxygen to form carbon dioxide, water and energy. Apart from other functions, this energy maintains our body heat.
C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) + Energy
Due to this production of energy, respiration is considered an exothermic process.
Page No 18:
Question 2:
On what basis is a chemical equation balanced?
ANSWER:
A chemical equation is balanced on the basis of law of conservation of mass; it states that "matter can neither be created nor be destroyed". If numbers of atoms of various elements are different in reactants' and products' side, it means they are either destroyed or created, which violate the law of conservation of mass.
Page No 18:
Question 3:
What happens chemically when quicklime is added to water filled in a bucket?
ANSWER:
When quicklime (calcium oxide) is added to water filled in a bucket, they react chemically to form slaked lime (calcium hydroxide) and produce heat energy. So, water in the bucket becomes hot.
CaO (s) + H2O (l) → Ca(OH)2 (aq) + Heat
Calcium oxide Water Calcium hydroxide
Page No 18:
Question 4:
Why should magnesium ribbon be cleaned before burning in air?
ANSWER:
Magnesium ribbon should be cleaned before burning in air to remove the basic magnesium carbonate coating on it. This layer should be removed so that the ribbon may readily combine with oxygen while burning in air. Basic magnesium carbonate layer consists of magnesium carbonate and magnesium hydroxide.
Page No 18:
Question 5:
State whether the following statement is true or false:
A chemical equation can be balanced easily by altering the formula of a reactant or product.
ANSWER:
False
Formula of a reactant or product cannot be altered, but chemical equation is balanced by multiplying the reactant or product with numbers like 2,3,4,5 and so on to balance the number of atoms in the chemical equation.
Page No 18:
Question 6:
What is wrong with the following chemical equation?
Mg + O → MgOCorrect and balance it.
ANSWER:
In this reaction, oxygen is written as O, but it is a diatomic molecule and its formula is O2.
The correct balanced chemical equation read as follows:
2Mg (s) + O2 (g) → 2MgO (s)
Page No 18:
Question 7:
What does the symbol (aq) represent in a chemical equation?
ANSWER:
The symbol (aq) stands for aqueous solution. When it is written after a formula in a chemical equation, it represents that the element or compound is a solution made in water.
Page No 18:
Question 8:
Why is photosynthesis considered an endothermic reaction?
ANSWER:
Photosynthesis is considered an endothermic reaction because in this process light energy from sunlight is absorbed to produce oxygen and glucose from carbon dioxide and water in the presence of chlorophyll.
Answer:
1. Respiration is considered as an exothermic process because in this reaction energy is released by the breakdown of glucose.
2. Chemical equation is balanced on the basis of the law of conservation of mass.
3. When quicklime (CaO) is added to water it reacts vigorously with it and forms slaked lime (Ca(OH)2) and produce a lot of heat.
4. Magnesium ribbon should be cleaned before being used in order to remove the layer of magnesium formed by reaction with the oxygen present in air and form magnesium oxide
5. The question is incomplete.
6. The things wrong with this equation is that:
(a) Oxygen is a diatomic gas. So, it will be written as O2.
The correct chemical equation is :
2Mg + O2 → 2 MgO
7. The symbol (aq) in a chemical equation means aquaous solution.