[1 Mark Question Answer]

Question 11 Mark

Select the odd one out and justify your answer.
Fe, Pb, Al and Zn

Answer

Pb
Lead reacts with dilute sulphuric acid or HCl and forms an insoluble coating of lead sulphate or lead chloride.
The others react with dilute sulphuric acid or HCl to liberate hydrogen.

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Question 21 Mark

Select the odd one out and justify your answer.
Fe, Zn, Cu and Mg

Answer

Cu
Metals more reactive than hydrogen can displace it from acids.

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Question 31 Mark

Select the odd one out and justify your answer.
$SO_2, H_2S, NH_{3,}$ and $CO_3$

Answer

$NH_3$ is basic in nature.

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Question 41 Mark

Select the odd one out and justify your answer.
Zn, Fe, Mg, and Na

Answer

Na
The other metals react with dil. HCl liberating hydrogen gas, while sodium reacts violently with acid.

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Question 51 Mark

Write the equation in the ionic form
$CuSO4_{(aq)}+ Fe_{(s)}→FeSO4_{(aq)}+ Cu_{(s)}$

Answer

Equation in the ionic form:
$Cu^{2+}{SO_4}^{2-}+ Fe→Fe^{2+}{SO_4}^{2-}+ Cu$

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Question 61 Mark

State whether the following conversion is oxidation or reduction:
$2Cl^--e^-→Cl_2$

Answer

Oxidation

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Question 71 Mark

State whether the following conversion is oxidation or reduction:
$K→K^++ e^-$

Answer

Oxidation

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Question 81 Mark

State whether the following conversion is oxidation or reduction:
$Cu^{2+}+ 2 e^-→Cu$

Answer

Reduction

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Question 91 Mark

State whether the following conversion is oxidation or reduction:
$PbO_2+ SO_2→PbSO_4$

Answer

When there is an increase in the oxidation state, the compound is said to undergo oxidation.
When there is a decrease in the oxidation state, the compound undergoes a reduction.
$PbO_2→$ Reduction, $SO_{2} →$ Oxidation.

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Question 101 Mark

State, giving reason, whether the substances printed in bold letters have been oxidized or reduced.
$Cl_2+ H_2S\rightarrow 2HCl + S$

Answer

Chlorine undergoes reduction by the addition of hydrogen to formHCl.

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Question 111 Mark

State, giving reason, whether the substances printed in bold letters have been oxidized or reduced.
$H_2S+ Cl_2\rightarrow 2HCl + S$

Answer

$H_2S$ undergoes oxidation by loss of hydrogen to give sulphur.

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Question 121 Mark

State, giving reason, whether the substances printed in bold letters have been oxidized or reduced.
$Mg +2HCl\rightarrow MgCl_2+ H_2$

Answer

Magnesium undergoes oxidation by loss of electrons $(Mg - 2e^-\rightarrow Mg^{2+}).$

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Question 131 Mark

State, giving reason, whether the substances printed in bold letters have been oxidized or reduced.
$PbO+ CO\rightarrow Pb+ CO_2$

Answer

PbO in the given reaction is reduced to Pb by losing oxygen.

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Question 141 Mark

Name:
a solid that is an oxidizing agent.

Answer

$MnO_2$

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Question 151 Mark

Name:
a gas that is oxidizing as well as a reducing agent.

Answer

Hydrogen gas

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Question 161 Mark

Name:
a liquid that is an oxidizing agent as well as a reducing agent.

Answer

Water

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Question 171 Mark

Name:
a substance that will reduce aqueous Iron(III)ions to iron(II)ions.

Answer

zinc

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Question 181 Mark

Name:
a substance that oxidizes concentrated $HCl$ to chlorine.

Answer

$MnO_2$
manganese(IV) oxide

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Question 191 Mark

Name:
an oxidizing agent that does not contain oxygen.

Answer

Chlorine

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Question 201 Mark

Correct the following statement: Conc. $H _2 SO _4$ reacts with zinc to liberate hydrogen.

Answer

Dil. $H _2 SO _4$ reacts with zinc to liberate hydrogen.

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Question 211 Mark

Correct the following statement:
Very dilute nitric acid reacts with iron to produce hydrogen.

Answer

Very dilute nitric acid reacts with magnesium and manganese to produce hydrogen.

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Question 221 Mark

Correct the following statement:
Hydrogen is dried by passing it through conc. $H_2SO_4$.

Answer

Hydrogen is dried by passing it through calcium chloride, caustic potash, and phosphorous pentoxide.

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Question 231 Mark

Correct the following statement:
All metals react with acids to give hydrogen.

Answer

All metals above hydrogen in the activity series react with acids to give hydrogen.

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Question 241 Mark

Correct the following statement:
Hydrogen is separated from CO by passing the mixture through caustic potash solution.

Answer

Hydrogen is separated from $CO _2$ by passing the mixture through caustic potash solution.

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Question 251 Mark

Based on the reactions of water on metals, arrange the following metals in increasing order of reactivity: iron, sodium, magnesium, zinc, calcium

Answer

Increasing order of reactivity of metals:
Iron < Zinc < Magnesium < Calcium < Sodium

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Question 261 Mark

Why are the following metals not used in the lab. preparation of hydrogen?
sodium

Answer

Sodium reacts violently with acid.

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Question 271 Mark

Why are the following metals not used in the lab.preparation of hydrogen?
aluminium

Answer

Aluminium forms a protective coating of $Al_2O_3$ due to its great affinity for oxygen. So, it does not give hydrogen with acid after the reaction has occurred for some time.

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Question 281 Mark

Why are the following metal not used in the lab.preparationof hydrogen?
iron

Answer

Iron has to be heated, and hydrogen thus produced contains impurities such as hydrogen sulphide and sulphur dioxide.

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Question 291 Mark

Why are the following metals not used in the lab preparation of hydrogen?
calcium

Answer

Calcium is expensive.

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Question 301 Mark

Hydrogen may be prepared in the laboratory by the action of a metal on an acid.
How would you modify your apparatus to collect dry hydrogen? Which drying agent would you employ for this purpose?

Answer

The gas is collected by the downward displacement of water.
Common drying agents such as fused calcium chloride, caustic potash stick and phosphorus pentoxide remove water vapor.

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Question 311 Mark

Hydrogen may be prepared in the laboratory by the action of a metal on an acid.
Which of the metals copper, zinc, magnesium or sodium would be the most suitable?

Answer

Zinc is the most preferred metal in the laboratory preparation of hydrogen.

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Question 321 Mark

Which metal is preferred for collecting hydrogen from:
Write the balanced equation
Steam

Answer

Steam:Aluminium
$3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$

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Question 331 Mark

Which metal is preferred for collecting hydrogen from:
Write thebalanced equation
Hot water

Answer

Hot water: Magnesium
$Mg_{(s)} + 2H2O_{(l)} \rightarrow Mg(OH) _{2(s)} + H_{2(g)}$

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Question 341 Mark

Which metal is preferred for collecting hydrogen from Cold water?Write the balanced equation.

Answer

Cold water: Calcium
$\mathrm{Ca}+2 \mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{Ca}(\mathrm{OH})_2+\mathrm{H}_2$

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Question 351 Mark

Hydrogen can be prepared with the help of cold water. Give a reaction of hydrogen with:
A divalent metal

Answer

$Ca + 2H_2O \rightarrow Ca(OH)_2+ H_2$

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Question 361 Mark

Hydrogen can be prepared with the help of cold water. Give a reaction of hydrogen with:
Amonovalent metal

Answer

$2K + 2H_2O \rightarrow 2KOH + H_2$

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Question 371 Mark

Under what conditions can hydrogenbe made to combine with oxygen?
Name the products and write the equation for the reaction.

Answer

Hydrogen burns in the presence of electric spark with a 'pop' sound in oxygen and with a blue flame forming water.
$2H_2+ O_2\rightarrow 2H_2O$

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Question 381 Mark

Under what conditions can hydrogenbe made to combine with sulphur?
Name the products and write the equation for the reaction.

Answer

Hydrogen gas on passing through molten sulphur reacts to give hydrogen sulphide.
$H_2+ S \rightarrow H_2S$

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Question 391 Mark

What do you observe when hydrogen gas is passed through a soap solution?

Answer

On passing hydrogen gas through soap solution, soap bubbles filled with hydrogen fly high and burst. This behavior proves that hydrogen is lighter than air.

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Question 401 Mark

Write a balanced equation for the reaction named metal with (i) boiling water (ii) steam.

Answer

$Mg + 2H_2O \rightarrow Mg(OH)_2+ H_2$
$Mg + H_2O \rightarrow MgO+ H_2$

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Question 411 Mark

Metal in the powdered form reacts very slowly with boiling water, but it decomposes in steam. Name the metal.

Answer

Magnesium

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Question 421 Mark

How did the name 'hydrogen' originate?

Answer

The name 'hydrogen' originated on account of its ability to form water.

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Question 431 Mark

A small piece of calcium metal is put into a small trough containing water. There is effervescence and white turbidity is formed.
Write an equation for the reaction.

Answer

$Ca + 2H_2O \rightarrow Ca(OH)_2+ H_2$
The solution turns blue.

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Question 441 Mark

A small piece of calcium metal is put into a small trough containing water. There is effervescence and white turbidity is formed.
Name the gas formed in the reaction. How would you test the gas?

Answer

Hydrogen gas. When red litmus is introduced in the solution, it turns blue.

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Question 451 Mark

Give an equation to express the reaction between:
Calcium and water

Answer

$Ca + 2H_2O⇋Ca(OH)_2+ H_2$

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Question 461 Mark

Give an equation to express the reaction between:
Steam and red hot iron

Answer

$3Fe + 4H_2O⇋Fe_3O_4+ 4H_2$

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Question 471 Mark

Hydrogen is manufactured by the 'Bosch Process'.
How can you obtain hydrogen from a mixture of hydrogen and carbon monoxide?

Answer

The mixture is passed through an ammoniacal cuprous chloride solution in order to dissolve any uncombined carbon monoxide.
$\mathrm{CuCl}+\mathrm{CO}+2 \mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{CuCl} \cdot \mathrm{CO} \cdot 2 \mathrm{H}_2 \mathrm{O}$

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Question 481 Mark

Which test should be made before collecting hydrogen in a gas jar?

Answer

Test: Collect some amount of gas in a test tube and take it to a flame.
If the gas burns quietly, then there is no more air in the flask.

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Question 491 Mark

Name the impurities present in hydrogen prepared in the laboratory.

Answer

Hydrogensulphide,sulphurdioxide, oxides of nitrogen,phosphine, arsine, carbon dioxide and watervapourare impurities present in the laboratory.

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Question 501 Mark