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CBSE Questions for Class 10 Chemistry Carbon And Its Compounds Quiz 9 - MCQExams.com
CBSE
Class 10 Chemistry
Carbon And Its Compounds
Quiz 9
______ is the perfectly crystalline allotrope of carbon.
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Coal
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Coke
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Diamond
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Wood
Explanation
Different physical forms of the same element in which it can exist are called allotropes. Besides graphite, the other allotropes of crystalline carbon are diamond and fullerenes
Hence, the correct option is $$C$$.
Graphite is a conductor of electricity because
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it has free valence electrons.
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it is a non-metal form of carbon.
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it is an allotrope of carbon.
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Both A and B.
Explanation
Graphite is a conductor of electricity because as can be seen in the crystal structure of graphite (in the figure) it has free valence electrons which can conduct electricity.
Graphite displays the property of both metal and non-metal. As a metal, graphite is a good conductor of electricity due to the mobility of electrons in outer valence shells.
An element $$X$$ has $$6$$ electrons in its outermost shell. Then the number of electrons shared by $$X$$ with another atom to form a covalent bond is:
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$$3$$
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$$2$$
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$$6$$
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$$4$$
Explanation
No. of electrons in the outermost shell of an element $$X=6$$
$$\therefore$$ In a covalent bond, we share one/more electron pairs.
So, to form a covalent bond, it needs one pair of electrons(2 electrons) to complete its octet.
Hence, option B is correct.
$$CH_4$$ is a /an _____________ compound.
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Ionic
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Covalent
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Both a and b
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None of these
Explanation
$$CH_{4}$$ is correct covalent compound as it is formed by sharing of $$e^{-}$$.
The formula of methane is $$CH_4$$ and its succeeding member ethane is expressed in $$C_2 H_6$$. The common difference of succession between them is:
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$$CH_2$$
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$$C_2H_2$$
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$$CH_4$$
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None of the above
Explanation
Methane and ethane are alkanes. These are saturated carbon compounds. They have the general formula $$C_nH_{2n+2}$$. All the alkanes differ by $$CH_2$$ group successively in the series.
Among the given compounds, which can have triple bond?
$$C_2H_4$$, $$C_3H_4$$, $$C_3H_6$$.
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$$C_2H_4$$
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$$C_3H_4$$
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$$C_3H_6$$
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All of these
Valency of carbon is:
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1
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4
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3
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2
Explanation
Hint:
Valency of carbon can be defined as combining power with hydrogen.
Explanation:
The number of valence electrons in the outermost shell in carbon is
$$4$$.
To attain noble gas configuration carbon makes
$$4$$
bonds with carbon.
Therefore, Carbon is tetravalent.
Hence, correct option is
$$4$$.
In a covalent bond formation:
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transfer of electrons takes place
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sharing of electrons between two atoms takes place
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electrons are shared by one atom only
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electrons are donated by one atom and shared by both atoms.
Explanation
Covalent bonds are formed when two atoms begin sharing electrons, the electrons are attracted towards the nuclei that are positively charged. Example: $$Cl-Cl$$.
It is not necessary that both atoms of covalent bond always will be the same, they can be different for example $$HF$$ molecule, in such case electrons not shared equally and attract towards the more electronegative element.
$$C_{3}H_{6}, C_{4}H_{8}$$ and $$C_{5}H_{10}$$ belong to the same homologous series. The melting and boiling points of $$C_{5}H_{10}$$ are higher than that of $$C_{4}H_{8}$$.
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True
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False
Explanation
$$C_{3}H_{6}, C_{4}H_{8}$$ and $$C_{5}H_{10}$$ belong to the same homologous series because each compound differs by $$-CH_2-$$ units with the preceding one and each compound belongs to the same functional group.
In homologous series, the molecular masses of succeeding members are higher than the preceding members. As the molecular masses increases, the melting and boiling points also increase. So, melting and boiling points of $$C_5H_{10}$$ are higher than the others in the given series.
The chlorination of methane is an example of:
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addition
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elimination
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substitution
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None of the above
Explanation
Saturated hydrocarbons are fairly unreactive and are inert in the presence of most reagents. However, in the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. It is called a substitution reaction because one type of atom or a group of atoms takes the place of another.
$$\displaystyle CH_4 + Cl_2 \xrightarrow {h \nu} CH_3-Cl + HCl$$
In the given figure label the parts.
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A - Hydrophilic tail, B - hydrophobic head
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A - Hydrophobic tail, B - hydrophobic head
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A - Hydrophobic tail, B - hydrophilic head
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A - Hydrophilic tail, B - hydrophilic head
Washing soaps produce scum with hard water and not much foam because hard water contains:
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chalk and sulphur
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many dissolved inorganic salts
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many suspended particles
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organic matter
Explanation
Hard water contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulfates. Ferrous ion may also be present, oxidized to the ferric form. It appears as a reddish-brown stain on washed fabrics and enameled surfaces. Water hardness that is caused by calcium bicarbonates is known as temporary because boiling converts the bicarbonates to the insoluble carbonates, hardness from other salts is called permanent. Calcium and magnesium ions in hard water react with the higher fatty acids of soap to form an insoluble gelatinous curd, thereby causing a waste of the soap.
A group closely related compounds which can be expressed by a general formula & in which two consecutive members differ by $$14$$ in their molecular masses is called:
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a heterogeneous series
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a homologous series
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a homogeneous series
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a electrochemicals series
Explanation
In homologous series, the two consecutive members will differ by 14 units in their molecular masses.
Ex-
Alkanes, Alkenes, Alkynes $$\rightarrow$$ Two consecutive units of any of the homologous series, (i.e., alkanes, alkenes, alkynes), are differ by 1 $$C{H}_{2}$$ unit or by 14 units in their molecular masses.
In homlogous series, successive members differ by:
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$$CH_{3}-$$
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$$CH_{3}-CH_{2}-$$
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$$-CH_{2}-$$
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$$-H$$
Explanation
A homologous series is a series of compounds in which each member differs from the next/previous by $$-C{ H }_{ 2 }-$$ or 14 mass units.
Physical properties change in members of homologous series but chemical properties remain almost the same because the functional group remains the same.
In the presence of the acid catalyst, ethanoic acid reacts with ethanol to produce________.
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ethanol
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ethanoic
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ethyl ethanote
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ethyl ethanol
Explanation
$$CH_3COOH + CH_3CH_2OH \xrightarrow{H^+} CH_3COOC_2H_5$$
$$Ethanoic \ acid$$ $$Ethanol$$ $$Ethyl \ ethanoate$$
The reaction between acid and alcohol produces ester and the reaction is known as esterification
Hence, this is an acid catalysed esterification reaction.
$$CH_3$$ $$CH_3$$
$$H_3C-CH_2-\overset {|}{CH}-\overset {|}{CH}-CH_3$$
Write the IUPAC name of the given compound.
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2,3-dimethylpentane
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3,4-dimethylhexane
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2-sec-butylbutane
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2,3-dimethylbutane
Explanation
$$CH_3$$ $$CH_3$$
$$H_3\underset {5}C-\underset {4}CH_2-\overset {|}{\underset {3}CH}-\overset {|}{\underset {2}CH}-\underset {1}CH_3$$
Numbering the longest carbon chain, and considering that two methyl groups are attached at second and third carbon, we get IUPAC name as $$2,3-dimethylpentane$$.
$$H - \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} - \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} - \underset{\!\!OH}{\underset{|}{\overset{H}{\overset{|}{C}}} - }H$$ $$H - \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} - \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} - OH$$ $$H - \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} - \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} - H$$ $$\underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}} = \underset{H}{\underset{|}{\overset{H}{\overset{|}{C}}}}$$
$$(1)$$ $$(2)$$ $$(3)$$ $$(4)$$
The structures of four molecules are shown.
Which molecules belong to the same homologous series?
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$$1$$ and $$2$$
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$$1$$ and $$3$$
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$$2$$ and $$4$$
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$$3$$ and $$4$$
Explanation
Molecules $$1$$ and $$2$$ contain the same functional group, i.e., alcohol, and their formula differs by $$CH_2$$ group. Thus belongs to the same homologous series while compound $$3$$ and $$4$$ belongs to alkane and alkene respectively.
A homologous series is a group or class of compounds having the same general formula and similar chemical properties in which successive members differ by $$-CH_2$$ group.
Hence, option A is correct.
Which pollutant gas can be produced as a result of incomplete combustion of octane ($${C}_{8}{H}_{18}$$)?
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Carbon
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Carbon dioxide
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Carbon monoxide
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Methane
Explanation
When the supply of air is poor then incomplete combustion takes place which forms carbon monoxide instead of carbon dioxide.
The balanced chemical equation for this reaction is;
$$2C_8H_{18} + 17O_2 \rightarrow 16CO + 18H_2O$$
_________ is/are a major component of shampoos and soaps.
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$$Li$$
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$$Na$$
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$$K$$
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$$Fr$$
Explanation
Soaps
are
sodium
or
potassium
salts of
fatty acids.
Which pair of statements about diamond and graphite is correct?
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Diamond and graphite are both pure carbon. They are both macromolecules.
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Diamond and graphite can both be used as electrodes. Graphite is also used as a lubricant
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Diamond has covalent bonds. Graphite has ionic bonds.
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Diamond is hard with a high melting point. Graphite is soft with a low melting point.
Explanation
Diamond and graphite are macromolecules and contain only carbon. Both are the allotropes of carbon.
Graphite is a good conductor of electricity thus used as an electrode.
Diamond is a bad conductor of electricity thus not used as an electrode.
Both Diamond and Graphite have a covalent bond.
Graphite has a melting point similar to that of diamond of around 3600°C, at which it sublimes rather than melting.
Hence option A is correct.
Which statement about bonding is not correct?
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Carbon can form covalent bonds.
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Chlorine atoms react to gain a noble gas electronic configuration.
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Covalent bonding involves losing and gaining electrons.
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Hydrogen molecules have the formula $$H_{2}$$.
Explanation
Covalent bonding involves sharing of electrons. Losing and gaining of electrons is found in ionic bonding.
State whether the following statement is true or false :
A soap contains only hydrophilic part while a detergent consist only hydrophobic part in the molecule.
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True
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False
Explanation
The action of soaps and detergents is based on the presence of both hydrophobic and hydrophilic groups in the molecule and this helps to emulsify the oily dirt and hence its removal.
Therefore it is clear from the above statement that both soap and a detergent contain hydrophilic as well as a hydrophobic part in their molecules.
Hence given statement is wrong.
Soap are the salts of higher fatty acids.
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True
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False
Explanation
Soap is a salt formed by the reaction between a higher fatty acid and a strong alkali.
Hence the given statement is true.
Soft soap are
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Sodium salt
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Calcium salt
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magnesium salt
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potassium salt
Explanation
Softsoap is semi-liquid or easily soluble soap made by saponification with potassium hydroxide instead of the more typical sodium hydroxide. Hence option (D) is correct.
Soaps are sodium or potassium salts of carboxylic acids.
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True
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False
Explanation
Soaps are sodium or potassium salts of long-chain carboxylic acids.
State whether the following statement is True or False;
Tartaric acid has two asymmetric carbon atoms.
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True
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False
Explanation
It has two asymmetric carbon atoms $$C_2$$ and $$C_3$$.
Rectified spirit is a mixture of:
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95% ethyl alcohol + 5% water
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94% ethyl alcohol + 4.53% water
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94.4% ethyl alcohol + 5.43 % water
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95.57% ethyl alcohol + 4.43% water
Explanation
Rectified spirit, also known as neutral spirits, rectified alcohol, or ethyl alcohol.
95.5% ethanol with 4.5% water mixture called Rectified Spirit.
Hence, the answer is option $$D$$.
The complete combustion of hydrocarbon produces
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$$CO + H_2$$
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$$CO + N_2$$
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$$CO_2 + H_2O$$
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$$CO + N_2O$$
Explanation
The complete combustion of hydrocarbons produce carbon dioxide and water.
Example: $$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$$
When two pairs of electrons are shared, bond is
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Single covalent bond
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Double covalent bond
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Dative bond
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Triple bond
Explanation
Answer $$(B)$$ Double covalent bond
A Double covalent bond is formed when two pairs of electrons are shared
between the atoms rather than just one pair.
Identify the unsaturated compounds from the following
(i) Propane
(ii) Propene
(iii) Propyne
(iv) Chloropropane
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(i) and (ii)
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(ii) and (iv)
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(iii) and (iv)
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(ii) and (iii)
Explanation
Propene has one double bond, while propyne has one triple bond. Hence, they are unsaturated compounds.
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