[1 Mark Question Answer]

Question 11 Mark

4.5 moles of calcium carbonate are reacted with dilute hydrochloric acid.Write the equation for the reaction.

Answer

$CaCO _3+2 HCl \longrightarrow CaCl _2+ H _2 O + CO _2 \uparrow$

Question 21 Mark

Correct the following statement :
Equal masses of all gases under identical conditions contain the same number of molecules.

Answer

The correct statement is that equal volumes of all gases under identical conditions contain the same number of molecules.

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Question 31 Mark

A compound 'X' consists of 4.8% of C and 95.2% of Br by mass.
Name the type of chemical reaction by which X can be prepared from ethane.

Answer

This substance can be prepared by substitution method.

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Question 41 Mark

What is the vapour density of ethylene? $($Avogadro's number $= 6 \times 10^{23};$ Atomic weight of $C = 12, H = 1; $Molar volume $= 22.4$ litres at $ \text{STP})$

Answer

Vapour density $=$ Molecular weight$/ 2 = 28 / 2 = 14 .$

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Question 51 Mark

The volumes of gases A, B, C and D are in the ratio, 1:2:2:4 under the same conditions of temperature and pressure.
If this ratio of gas volumes refers to the reactants and products of a reaction, which gas law is being observed?

Answer

Gay -Lussac's law of combining volumes.

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Question 61 Mark

The volumes of gases A, B, C and D are in the ratio, 1:2:2:4 under the same conditions of temperature and pressure.
If the temperature and the pressure of gas A are kept constant then what will happen to the volume of A when the number of molecules is doubled?

Answer

If the temperature and the pressure of gas $A$ are kept constant, then the volume of the gas will get doubled.

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Question 71 Mark

The volumes of gases A, B, C and D are in the ratio, 1:2:2:4 under the same conditions of temperature and pressure.
Which sample of gas contains the maximum number of molecules?

Answer

Gas D contains the maximum number of molecules.

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Question 81 Mark

A flask contains 3.2g of sulphur dioxide. Calculate the following : The volume occupied by 3.2g of sulphur dioxide at STP.

Answer

64g of SO2 occupy a volume= 22.4L
So, 3.2g of SO2 will occupy a volume = 22.4 x 3.2/64 = 1.12L

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Question 91 Mark

A flask contains 3.2g of sulphur dioxide.Calculate the following : The moles of sulphur dioxide present in the flask.

Answer

Moles = Weight of substance in grams/ molecular weight
So, Moles of SO2 = 3.2/64 = 0.05

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Question 101 Mark

A flask contains $3.2g$ of sulphur dioxide. Calculate the following: The number of molecules of sulphur dioxide present in the flask.

Answer

Number of molecules $= Moles \times 6.023 \times 10^{23}$
So, number of molecules of $SO_2 = O.O5 \times 6.023 \times 10^{23}$
$= 0.30115 \times 10^{23}$
$= 0.302 \times 10^{23}$

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Question 111 Mark

Samples of the gases $O_2, N_2, CO_2$ and $CO$ under the same conditions of temperature and pressure contain the same number of molecules represented by $X.$ The molecules of Oxygen, occupy $V$ litres and have a mass of $8 \ g.$ Under the same conditions of temperature and pressure:
In answering the above questions, which law have you used?

Answer

Avogadro's law

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Question 121 Mark

Samples of the gases $O_2, N_2, CO_2$ and $CO$ under the same conditions of temperature and pressure contain the same number of molecules represented by $X.$ The molecules of Oxygen, occupy $V$ litres and have a mass of $8 g$. Under the same conditions of temperature and pressure :
What is the volume occupied by $: 3X$ molecules of $CO$? $[C=12,N=14,O=16]$

Answer

$3X$ molecules of $CO$ occupies $3V$ litres.

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Question 131 Mark

Samples of the gases $O_2, N_2, CO_2$ and $CO$ under the same conditions of temperature and pressure contain the same number of molecules represented by $X$. The molecules of Oxygen, occupy $V$ litres and have a mass of $8 g.$ Under the same conditions of temperature and pressure :
What is the volume occupied by $: X$ molecules of $N_{2.}$

Answer

$X$ molecules of $N_2$ occupies $V$ litres.

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Question 141 Mark

Mention the term defined by the following sentence:
The mass of a given volume of gas compared to the mass of an equal volume of hydrogen.

Answer

The term is vapour density.

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Question 151 Mark

When gases react their volumes bear a simple ratio to each other, under the same conditions of temperature and pressure. Who proposed this gas law?

Answer

Gay - Lussac proposed this law.

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Question 161 Mark

Calculate the weight of one molecule of oxygen .
$[$Avogadro's number $= 6 \times 1023, O = 16 ]$

Answer

Weight of $6 \times 10^{23}$ molecules of oxygen $= 32g$
Weight of $1$ molecule of oxygen $= 32/ 6 \times 10^{23} = 5.33 \times 10^{23}g.$

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Question 171 Mark

Calculate the relative molecular mass of Potassium chlorate.
$($use $K = 39, Cl = 35.5, O = 16, C = 12, H = 1, Na = 23, N = 14, S=32)$

Answer

The relative molecular mass of Potassium chlorate $(KCIO_{3)}$ is
$[$atomic mass of $1K$ atom $+$ Atomic mass of $1 \ Cl$ atom $+$ atomic mass of $3 \ O$ atoms$]$
$39+ 35.5 + 16 \times 3 = 122 .5$

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Question 181 Mark

What is the value of Avogadro's number?

Answer

The value of Avogadro's number is $6.023 \times 10^{23}.$

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Question 191 Mark

Define atomicity of a gas.

Answer

Atomicity of a gas : The number of atoms in a molecule of a gas is called its atomicity.
For example : Monoatomic means a gas molecule containing one atom. Similarly diatomic corresponds to two atoms and triatomic corresponds to three atoms in a molecule of a gas.

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Question 201 Mark

State: Avogadro's law

Answer

Avogadro's law : It states that 'Under the same conditions of temperature and pressure, equal volumes of all gases contain the same number of molecules'.

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Question 211 Mark

State: Gay-Lussac's law of combining volumes.

Answer

When gases react, they do so in volumes which bear a simple ratio to one another and to the volume of the gaseous product, if all the volumes are measured at the same temperature and pressure.

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Question 221 Mark

Give example of compound whose:
Empirical formula is different from the molecular formula.

Answer

$C_6H_{12}O_6.$

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Question 231 Mark

Give example of compound whose:
Empirical formula is the same as the molecular formula.

Answer

$Na_2SO_4.10H_2O.$

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Question 241 Mark

Prove the Following : Oxygen is a diatomic molecule.

Answer

Since one Oxygen molecule contains $2$ atoms of oxygen, so it is a diatomic molecule. $O + O \rightarrow O_2$

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Question 251 Mark

Give the empirical formula of: $CH_3COOH$

Answer

The empirical formula of $CH_3COOH$ is: $CH_2O.$

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Question 261 Mark

Give the empirical formula of : $C_2H_2$

Answer

The empirical formula of $C_2H_2$ is: $CH$

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Question 271 Mark

Give the empirical formula of: $C_6H_{12}O_6$

Answer

The empirical formula of $C_6H_{12}O_6$ is : $CH_2O.$

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Question 281 Mark

Give the empirical formula of : $C_6H_6$

Answer

The empirical formula of $C_6H_6$ is: $CH$

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Question 291 Mark

Give one word or phrase for the following:
Formation of ions from molecules.

Answer

Ionisation

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Question 301 Mark

Give one word or phrase for the following:
The ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen under the same conditions of temperature and pressure.

Answer

Vapour density

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Chemistry [1 Mark Question Answer]

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