Catalysts are the substances that are used to alter the rate of a chemical reaction without themselves being affected. They either increase the rate of a chemical reaction or decreases the rate of a chemical reaction. This process is known as catalysis. Catalysts that increase the rate of a chemical reaction are positive catalysts, whereas the catalysts which decrease the rate of a chemical reaction are negative catalysts.

Balance the following chemical equations: (a) H 2 + O 2 → H 2 O (b) MnO 2 + HCl → MnCl 2 + Cl 2 + H 2 O

A chemical equation in which the number of atoms of each element is equal on both sides of the equation is known as a balanced chemical equation. (a) When hydrogen reacts with oxygen, water is formed. The balanced chemical equation is as follows: 2 H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) (b) Manganese dioxide reacts with hydrochloric acid and forms manganese chloride, chlorine gas and water. The balanced chemical equation is as follows: MnO 2 s + 4 HCl aq → MnCl 2 s + Cl 2 g + 2 H 2 O l

Balance the following chemical equations: (a) Na + O 2 → Na 2 O (b) K + H 2 O → KOH + H 2

(a) A balanced chemical equation is a chemical equation where the number of atoms involved in the reactants side is equal to the number of atoms on the products side. The balanced chemical equation for the given equation is: 4 Na + O 2 → 2 Na 2 O Sodium is a very reactive metal, it tends to react with oxygen to form sodium oxide. (b) The balanced chemical equation for the given equation is: 2 K + 2 H 2 O → 2 KOH + H 2 This is a single replacement reaction where the potassium atom replaces the hydrogen in H 2 O .

In the following chemical equations: C + O 2 → CO 2 . . . . . . . . . . . . . . . . i 2 H 2 O → Electric current 2 H 2 + O 2 . . . . . . . . . . . . . ii (iii) Write one difference between catalytic inhibitor and catalytic promoter.

Catalytic inhibitor are the substance which decrease the reaction rate by lowering the activity of the catalyst while the catalytic promoters are the substances which are used to increase the catalytic activity of a given catalyst.

Match List - I with List - II List - I (process) List - II (catalyst) (a) Deacon's process (i) ZSM - 5 (b) Contact process (ii) CuCl 2 (c) Cracking of hydrocarbons (iii) Ni (d) Hydrogenation of vegetable oils (iv) V 2 O 5 Choose the most appropriate answer from the options given below-

a - ii , b - iv , c - i , d - iii

a - i , b - ii , c - ii , d - iv

a - iii , b - i , c - iv , d - ii

a - iv , b - ii , c - i , d - iii

A catalyst is an agent that alters the rate of a chemical reaction without undergoing any permanent chemical change in the reaction. For example, nickel, platinum or palladium is used as a catalyst in the hydrogenation reaction of unsaturated compounds.

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Define catalysts.

Important Questions on Chemical Reactions and Equations

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Why should a magnesium ribbon be cleaned before burning in air?

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Two chemical mixed by the laboratory assistant in the laboratory are Barium chloride and potassium sulphate. Write a balanced Chemical Equation for the above reaction.

MEDIUM

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Balance the following chemical equations:

(a) $H_{2} + O_{2} \to H_{2} O$

(b) ${MnO}_{2} + HCl \to {MnCl}_{2} + {Cl}_{2} + H_{2} O$

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Translate the following statement into a chemical equation and balance it:

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

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N_{2} (g) + 3 H_{2} (g) \overset{Fe / Mo}{\to} 2 {NH}_{3} (g)

. Mo in the given reaction is

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Translate the following statement into a chemical equation and balance it:
Zinc reacts with sulphuric acid to give zinc sulphate and hydrogen gas.

HARD

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Balance the following chemical equations:

(a) $Na + O_{2} \to {Na}_{2} O$

(b) $K + H_{2} O \to KOH + H_{2}$

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Translate the following statement into chemical equation and then balance them.

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

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A student was performing an experiment to understand the enzyme-substrate reaction. The student measured the formation of coloured product using a colorimeter. The student plotted the graph below which shows the reaction rate versus the substrate concentration.

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Following interpretations were drawn by the student:
A. The higher concentration of substrate acts as an enzyme inhibitor.
B. It is sigmoidal curve with sharp transition from low to high reactions rates over the increasing substrate concentration.
C. The curve reaches a plateau and does not further increase with increasing substrate concentrations due to saturation of enzyme with the substrate.
Choose which of the interpretations of the graph are correct.

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Which one of the following statements is incorrect about enzyme catalysis?

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Why should a magnesium ribbon be cleaned before burning in the air?

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Science>Chemistry>Chemical Reactions and Equations>Chemical Changes and Equations

In the following chemical equations:

$C + O_{2} \to {CO}_{2} . . . . . . . . . . . . . . . . (i) 2 H_{2} O \overset{Electric current}{\to} 2 H_{2} + O_{2} . . . . . . . . . . . . . (ii)$

(iii) Write one difference between catalytic inhibitor and catalytic promoter.

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Translate the following statement into a chemical equation and then balance it.

Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.

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Translate the following statement into chemical equation and balance it:
Hydrogen gas combines with nitrogen to form ammonia.

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Translate the following statement into a chemical equation and then balance it.

Hydrogen gas combines with nitrogen to form ammonia.

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Which of the following is a correct balanced equation?

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Translate the following statement into chemical equation and then balance them.

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

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Match List $- I$ with List $- II$

	List $- I$ (process)		List $- II$ (catalyst)
(a)	Deacon's process	(i)	$ZSM - 5$
(b)	Contact process	(ii)	${CuCl}_{2}$
(c)	Cracking of hydrocarbons	(iii)	$Ni$
(d)	Hydrogenation of vegetable oils	(iv)	$V_{2} O_{5}$

Choose the most appropriate answer from the options given below-

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What is a catalyst?

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Write any one difference between the following: (i) Positive and Negative catalyst

Define catalysts.

Important Questions on Chemical Reactions and Equations

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