Chapter-3 Atoms and Molecules NCERT Exampler

Explanation:

 (d) (ii) and (iv)

Water mass divided by its molar mass equals the number of moles.

360 g / 18 g/mol = number of moles

There are 20 moles.

20 × 6.022 x 1023 = 1.2044 x 1025 water molecules make up the total number of molecules.

Option (d) is correct as a result.

Explanation:

The correct response is (a) Atoms cannot exist independently.

Atoms cannot exist on their own. This is so that atoms can create stable, octet-fulfilled electrical configurations by either accepting or donating electrons, which can only happen when molecules are formed. Atoms therefore cannot coexist.

Explanation:

(b) N2

The chemical symbol for nitrogen gas is N2, despite the fact that nitrogen only occurs in molecules with two ions. Nitrogen has the chemical formula N. The chemical representation of nitrogen gas is N2. In nature, 80% of the air we breathe is composed of nitrogen. In the natural world, it is always found in diatomic form..

Explanation:

(d) Na 

As the term sodium is derived from the Latin word natrium, its chemical name is Na. The Latin word "natron" (natrium) is where the sign "Na" comes from (soda in English). English chemist Humphry Davy first identified sodium in caustic soda electrolysis in 1807. (NaOH).

Explanation:

(c): 2 moles of CaCO

C₁₂H₂₂O₁₁ has a molecular weight of 342 gm (12(12) + 22(1) + 11(16) gm).

It weighs 0.2 moles, or 0.2 x 342 g, or 68.4 g.

The molar mass of CO₂ is equal to 44gm (12 + 2(16) gm).

It weighs 2 moles, or 2 x 44, or 88gm.

CaCO3 weighs a molar mass of = 40 + 12 + 3(16) = 100gm.

200 gm is equal to 2 moles of it, or 2 x 100 gm.

H₂O's molecular weight is 2(1) + 16 = 18 grammes.

It weighs 10 moles, or 10 x 18 gm, or 180 gm.

Explanation:

(d)18g of CH4

Explanation: Molar mass = number of atoms in the molecule x mass of the material x NA (a) 18 g of water equals 18 times 3/18 NA = 3 NA

(b) 18 g of oxygen is equal to 18 x 2 /32 NA, or 1.12 NA

(c) 18 g of CO2 are equal to 18.x3/44 and 1.23 NA

(d) 18 g of CH4 equals 18 x 5/16 NA = 5.63 NA.

NA is equal to 6.02311023.

Explanation:

(c) 1g H2

Note: NA = 6.023×1023

The number of molecules is inversely correlated with molecular mass when the mass is constant. In other words, there will be fewer molecules overall, but more of them. 1 g of H2 = ½ x NA = 0.5 NA = 0.5 × 6.022 × 1023 = 3.011 × 1023 has the most molecules possible in 1 g.

Explanation:

a) 16/ 6.023 × 1023g

Atomic mass of oxygen is equal to its Avogadro number times its mass. The oxygen atomic mass is 16 g. 6. 023 10 23 is the Avagadro number. Hence, the mass of one oxygen atom is equal to 16 / 6. 023 10 23 g. As the mass of an oxygen atom is 16 / 6. 023 10 23 g, the correct answer is (A)

Explanation:

(a) is 6.68 1023.

11 oxygen atoms make up 1 mole of sucrose (C12H22O11), where NA = 6.023102

Sucrose (C12 H22 O11) has = 0.01 11 NA oxygen atoms per mole.

= 0.11 NA oxygen atoms

= 18 g/(1×2+ 16)gmol-1

=18 g /18 gmol-

= 1mol

1 NA atom of oxygen may be found in 1 mol of water (H2O)

Total oxygen atoms present =

Sucrose oxygen atom number plus water oxygen atom number = total oxygen atoms.

= 0.11 NA plus 1.0 NA equals 1.11 N

Avogadro's number for the number of oxygen atoms in the solution is 1.11

= 1.11 × 6.022 ×10”23 = 6.68 × 1023

Explanation:

correct option is (c) when energy is either given to or taken out from the system

Energy may be introduced into a system or removed from one to cause a change in the physical condition. This is due to the fact that altering energy also alters the strength of the forces that pull matter particles together, changing its physical states (such as its solid, liquid, or gaseous forms).

Explanation:

(b) BiPO4 is the correct chemical formula.it is csalled as bismith phosphate

Bismuth phosphate is the proper name and the accurate formula is BiPO4. As both ions in bismuth phosphate, Bi+3 and PO4-3, are trivalent, its chemical formula, BiPO4, is accurate (BiPO4). Salt is bismuth nitrate. Bismuth, a heavy metal, is present. Humans use bismuth nitrate to avoid kidney damage from cancer medications, bone marrow damage from radiotherapy, and a digestive tract infection (Helicobacter pylori, or H. pylori) that can cause ulcers.

Explanation:

CuBr2 is short for copper (II) bromide

 Al(NO3) is short for aluminium (III) nitrate,

Ca3(PO4)2 is short for calcium (II) phosphate

HgCl2 is short for mercury (II) chloride

Mg(CH3COO)2 is the chemical formula for magnesium acetate.

Explanation:

All of the compounds that may be created by mixing the ions Cu2+, Na+, Fe3+, Cl- SO4 -2, and PO4 -3 have the following chemical formulas:

• CCl2, CSo4, and CCu3(PO4)2

• Na2SO4, Na3PO4, and NaCl

• Fe(Cl3), Fe(SO4)3, and Fe(PO4)

  
  

Explanation:

a) Na is a cation while CH3COONa-CH3COO is an anion.

b) The anion Na is a cation in NaCl-Cl.

c) Due to their shared electrovalent link, both ions in H2 are cations.

d) NO3 is an anion in NH4NO3 the cation NH4

REASONS:

* Acetic acid has the condensed structural formula CH 3 COOH in order to indicate the order of bonding. The formula CH 3 COONa is more suitable than NaCH 3 COO because in the salt form, the cation is linked to the negative charge of the carboxylate group of the acetate ion rather than the methyl group.

* Sodium is an electropositive alkali metal. Chlorine, a nonmetal that is electronegative by nature, receives one valence electron while it loses one.

* One atom seems to give its electron to another atom via an ionic connection, which is a chemical relationship between two atoms. Yet, covalent bonds seem to entail two atoms exchanging electrons in order to achieve a more stable electron configuration. Covalent and ionic connections can coexist in some substances. These substances include polyatomic ions.

* An anion, the nitrate ion, and a cation, the ammonium ion (NH4+), make up the salt known as ammonium nitrate (NO3-). Strong ionic bonds hold the cation and anion together.

Explanation:

(a)Calcium fluoride and fluoride (CaF2)

(b) Hydrogen and sulphur, also known as hydrogen sulphide and H2S.

(c) Nitrogen and hydrogen, NH3, form ammonia.

(d) Carbon tetrachloride, a compound of carbon and chlorine (CCl4)

(e) The mixture of oxygen and sodium oxide (Na2O)

(f)CO2, CO2, carbon dioxide, and carbon monoxide all include carbon and oxygen.

Explanation:

1. The proper symbol for cobalt is co; cobalt CO

2. Carbon C is incorrect; the proper symbol is C

3. Aluminium AL is incorrect; the proper sign is Al

4. Helium He is the appropriate emblem.

5. Sodium So is incorrect; the proper sign is Na

Explanation:

(a)Ammonia is a compound having a chemical formula is NH3.the 2 molecules in it have a ratio of N: H=14:3

A trigonal pyramidal structure results from the nonbonding pair of electrons pushing away from the bonding pairs. The molecule will have a trigonal planar structure if the core atom, which lacks a lone pair, is connected to three additional atoms.

(b)Carbon monoxideis a compound having a chemical formula is CO.the 2 molecules in it having a ratio of C:O= 12:16=3:4

A metal's hydride or alkyl group is transferred to a bound carbon monoxide during migratory insertion. We should examine CO's interactions with transition metals as this reaction especially includes bound CO. Reviewing carbon monoxide's Lewis structure is a good place to start.

(c)Hydrogen chloride is a compound having a chemical formula is HCl.the 2 molecules in it having a ratio of H:Cl= 1:35.5

As a hydrogen halide, the substance hydrogen chloride has the chemical formula HCl. It is a colourless gas at room temperature that reacts with the water vapour in the air to produce white fumes of hydrochloric acid. In technology and industry, hydrochloric acid and hydrogen chloride gas are essential. The formula HCl is also frequently used to refer to hydrogen chloride in aqueous solution, which is what makes up hydrochloric acid..

(d)Aluminium fluoride is a compound having a chemical formula is AlF3.the 2 molecules in it having a ratio of Al:F=27:57=9:19

AlF3xH2O-based inorganic compounds are referred to as aluminium fluoride. These are all solids without colour. The process of making aluminium metal involves the usage of anhydrous AlF3. A few are found as minerals.

Explanation:

(a) CO3-2 – 1+3=4

(b) PO4-3 – 1+4=5

(c) P2O5 – 2+5=7

(d) CO – 1+1=2

Explanation:

A material's relative atomic or molecular mass is equal to one mole's weight in grammes.

The Avogadro number mass of a mole of neutrons is 1 g.

Molecular mass divided by NA equals 18/NA g of water.

The molar mass of water is 18.015 g/mol. Avogadro's number (NA), which is equal to 6.022 x 1023 mol-1, and the weight of one oxygen (15.999) were added together to calculate this. Water molecules weigh 18/NA g apiece, and the hydrogen atomic weight (1.008) was increased by two to arrive at the final answer.

The oxygen atom has 8 neutrons.

Oxygen's atomic number divided by its volume equals the amount of neutrons in oxygen.

The atomic weight of oxygen, which is 15.9994, rises as temperature rises.

Hence, the mass is 16

Neutron number is therefore equal to 16 - 8 = 8.

8 neutrons have a mass equal to 8 / Avogadro number (NA) g.

Water's neutron-induced mass fraction is equal to 8/18 g.

Explanation:

The capacity of a solute to dissolve in 100g of solvent is known as solubility. Temperature affects a solute's ability to dissolve in a particular solvent. The solubility of liquids and solids increases with temperature. Similar to liquids, gases become less soluble as temperature rises.

Ex: Hot water dissolves sugar more quickly than cold water.

Certainly, the temperature affects a substance's solubility. In general, solubility gets better with temperature rise. For instance, heated water dissolves sugar more completely than cold water. For some solutes, this might not be the case.

Explanation:

(a) F2

 Diatomic their atomicity is (2 atoms)

(b) NO2

 Triatomic their atomicity is (3 atoms)

(c) N2O

Triatomic their atomicity is (3 atoms)

(d) C2H6

 Polyatomic their atomicity is (8 atoms)

(e) P4

 Polyatomic their atomicity is (4 atoms)

(f) H2O2

 Polyatomic their atomicity is (4 atoms)

(g) P4O10

 Polyatomic their atomicity is  (14 atoms)

(H) O3

 Triatomic their atomicity is  (3 atoms)

(i) HCl

 Diatomic their atomicity is (2 atoms)

(j) CH4

Polyatomic their atomicity is (5 atoms)

(k) He

Monoatomic their atomicity is  (1 atom)

(l) Ag

Monoatomic their atomicity is (1 atom)

Explanation:

Heating:

Sugar dissolves into liquid form when heated because sucrose has a decomposition point and melting point between 190 and 192 degrees Celsius. The sugar will therefore develop a light brown colour. Sugar burns and turns black when heated further.

Salt reaches its melting point at 841 degrees Celsius, or 1545.8 degrees Fahrenheit. Nothing happens if we don't raise the temperature to that level.

Conductivity of electricity:

If the provided material is dissolved in water, we may test its electrical conductivity to determine if it is salt or sugar. It conducts electricity if it is salt. Salt (NaCl) conducts electricity because it contains both positive sodium ions and negative chloride ions. Yet, because sugar only contains positive ions, it cannot conduct electricity.

Explanation:

Magnesium has a molar atomic mass of 24 g/mol. Given mass + number of moles Atomic mass Mg moles = 12g in weight. 24g mol-1 equals 0.5 mol.

The magnesium ribbon weighs 12 g.

Magnesium's molecular weight is 24 g/mol.

The formula to get the amount of moles is

The formula for calculating moles is: number of moles = weight of the material molar mass of the substances = 12 / 24 = 1/ 2 = 0.5 mol.

Explanation:

a) The molecular mass of CO2 is equal to 12 + 2 x 16 = 12 + 32 = 44 g mol-1.

The mass of 5 moles of CO2 is 44 x 5 = 220 g.

The molar mass of water is also equal to 2x 1 + 16 = 18 g mol-1.

5 moles of water weigh 18 x 5 or 90 g.

The difference between 5 moles of CO2 and 5 moles of water has been established

b) Moles per atomic weight Equals number of moles

Ca has an atomic mass of 40 amu.

Moles per 240g of Ca metal (240/40 = 6)

240/24 Equals 10 moles of magnesium in 240g of metal.

Mg has an atomic mass of 24 amu.

Ratio 6:10

Explanation:

(a) CaCO3 

1) CaCO: 40 g of calcium is its molar mass

16 g is the molar mass of oxygen.

12 g is the molar mass of carbon.

As a result, the mass-based ratio will be = 40: 12: 48 = 10: 3: 12.

(b) MgCl2 

2) MgCl: A molar mass of 12 g of magnesium.

Chlorine's molar mass is 35.5 g.

As a result, the ratio by mass will be 12: 71.

(c) H2SO4 

3) H SO: 1 g of hydrogen has a molar mass.

32 g is the molar mass of sulphur.

16 g is the molar mass of oxygen.

Ratio by mass is therefore 2: 32: 64 = 1: 16: 32.

(d) C2H5OH 

4) For C H OH, the mass ratio is 24: 6: 16 = 12: 3: 8.

(e) NH3 

5) NH: 14 g of nitrogen has a molar mass.

Mass: Ratio = 14: 3

(f) Ca(OH)2

6) For Ca(OH), the mass ratio is 40: 32: 2 = 20: 16: 1.

Explanation:

111g equals 1 mole of calcium chloride.

222g of CaCl2 is therefore equal to 2 moles of CaCl2.

1 unit of the formula CaCl2 produces 3 ions.

Hence, 3 moles of ions will result from 1 mol of CaCl2. 32=6 moles of ions would result from 2 moles of CaCl2

Ion number Equals Ion mole number Avogadro number

= 6 × 6.022 ×102

= 36.132×1023

= 3.6132 × 1024 ions

Explanation:

Each sodium atom and ion has one extra electron. There would be a differential of 100 moles of electrons for each of the 100 moles of sodium atoms and ions.

100 moles of electrons weigh 5.48002 g.

1 mole of electron weighs 5.48002 grammes per 100 grammes.

One electron's mass is 5.48002 x 100, or 6.022 x 1023.

= 9.1 ×1028 g

= 9.1×10-31 kg

Explanation:

It is the most popular resource for repurposing elemental mercury and the traditional source of vermilion, a vivid red or scarlet colour, and other red mercury paints. In vein-filling minerals, cinnabar typically develops in areas with recent volcanic activity and alkaline hot springs.

One molecule of HgS contains one atom of Hg, while 232.6 grammes of HgS contain 200.6 grammes of Hg. The molar mass of HgS is equal to the sum of the molar masses of Hg and S, which are 200.6 and 32, respectively.

Mass of Hg in 225 g of HgS is therefore 200.6 X 225 / 232.6 = 194.04 g.

Explanation:

The weight of a mole of screws is 2.475 1024g or 2.475 1021 kg.

Earth's mass divided by the mass of a mole of screws equals 5.98 1024 kg. 2.475×1021 \s= 2.4 ×10

The mass of screws is 2.4 x 103 times that of the earth.

Compared to a mole of screws, the world is 2400 times heavier.

Explanation:

The amount of oxygen atoms in vitamin C is 2. 58 10 24. Step 2: To determine how many moles of oxygen there are in the sample: The number of particles + the amount of moles Number avogadro 2. 58 10 24 moles of oxygen are present in the atmosphere. 6. 022 × 10 23 n = 4. 28 mol Thus, the sample contains 4. 28 moles of oxygen atoms.

We are aware that 1 mole Equals 6.022 x 1023.

The number of moles is equal to the number of particles or the Avogadro Number, where n is 2.58 1024 or 6.022 1023, respectively.

Explanation:

As the masses of both containers are equal, the heavier container will be determined by the mass of its atoms.

5 moles of sodium atoms weigh ((523)g=115g in Krish's container.

5 moles of carbon atoms in Raunak's container weigh 60g (5 x 12)g.

∴ It weighs more in Krish's container.

Equivalent moles of various atoms have the same number of atoms in them (b).

There are 6.023 10 23 atoms in a mole.

Five moles of atoms make up each.

The total number of atoms is thus 5 6.023 10 23.

Explanation:

There are 1022 stars present.

Thus, the quantity of stars is equivalent to the quantity of particles.

The following formula is used to determine the number of moles in a star.

Amount of moles equals number of particles divided by 6.02 3 1023

Hence, the formula for calculating the amount of moles in a star is: number of stars / Avogadro number (10 22/6.023 1023 = 0.0166 moles).

Explanation:

Atoms gain or lose electrons in creating various compounds, resulting in the formation of electrically charged ions. Ionic compounds are those that are created by the attraction of cations and anions.

For instance, 2Na + Cl2 2Na+ Cl- 2NaCl (sodium chloride- common salt.)

As sodium is a group 1 metal, it forms a cation with +1 charge. Chlorine is a non-metal that can create an anion with a charge of -1.

Molecular compounds are those that result from the covalent bonding of uncharged ions, and the bonding that occurs between them is referred to as covalent bonding. The two atoms that make up a molecular complex share electrons, and the components are joined by covalent bonds.

Examples: 2C + O2 2CO ( Carbon monoxide)

Explanation:

One mole of aluminium weighs exactly 13 electron masses, 13 proton masses, and 14 neutron masses (Avogadro's constant).

Knowing that only electron transfers occur when atoms become ions, we may calculate the mass of Al+3 as follows: Al+3 = 10 electron masses, 13 proton masses, 14 neutron masses, and Avogadro's constant. The aluminium atom's mass is now 3 electrons more than that of the aluminium ion.

Aluminum atom mass minus aluminium ion mass is 3 times the mass of each electron multiplied by Avogadro's constant, which equals 27.3 times 10-28 times 6.023 times 1023 g, or 164.4 times 10-5 g, 1.644 times 10-3 g, or 0.0016 g.

Explanation:

Ag stands for silver, a chemical element with the atomic number 47 and the Latin name argentum, which means "bright" or "white" in Proto-Indo-European. It is a transition metal that is soft, white, and glossy and has the highest electrical, thermal, and reflectivity of any metal.

Silver mass equals m g

Gold weighs m/100g.

Total number of silver atoms = mass/atomic mass X NA = m/108NA Gold atom count is m/100 X 197.

Number of atoms in silver divided by the number of atoms in gold equals Au: Ag = m/ 100 X 197 X NA: m/ 108 NA = 108; 100197 = 108; 19700 = 1; 182.41

Explanation:

Methane has a molecular mass of 6.02 x 1023.

Hence Methane molecules amounting to 1.5 x 1020 = (1.5 x 1020 x 1) (6.02 x 1023) moles

equals 2.49 x 10–4 moles.

Methane (CH4) has a molar mass of 12 + 1/4, or 16 g.

Methane mass equals molar mass times the number of moles, or 16 x 2.49 x 10 -4, or 3.984 x 10-3 g. (This is the same mass as Ethane)

Ethane (C2H6) is equal to 12 + 1 6 30.

If there are 6.02 x 1023 molecules in 30 g of ethane

3.984 x 10 -3 g thus is (3.984 x 10-3 x 6.02 x 1023) 30.

= 8 × 1019 ethane molecules

Explanation:

90/100 = 0.9g of gold will be present in one gramme of gold sample.

Mass of gold / its atomic mass equals the amount of moles of gold.

= 0.9/19.7 = 0.0046

The number of NA atoms in one mole of gold is 6.022 x 1023.

0.0046 mole of gold will therefore contain = 0.0046 6.022.

= 2.77 × 1021

Explanation:

With the chemical formula NaCl, sodium chloride (often referred to as salt but also including other chemical salts) is an ionic substance that comprises ions of sodium and chloride in a 1:1 ratio. 100 g of NaCl comprises 39.34 g Na and 60.66 g Cl, with molar weights of 22.99 and 35.45 g/mol, respectively.

6.023 x 1023 molecules of NaCl are present in 58.5 g, translating to 12.046 x 1023 ions.

The number of ions in 5.85 g of NaCl is 5.85 x 12.046 x 1023/ 58.5 = 1.2046 x 1023 ions.

Explanation:

Atomic mass divided by weight equals the number of moles.

For N2

N2 in 100 gms is equal to 100/2 x 14 moles, or 100/28 moles

Molecule count = 100 / 28 x 6.022 x 1023

N2's molar mass is equal to twice that of monoatomic N.

N2 has a molecular mass of 2 x 14.0067, or 28 moles.

Molecule count = 100/28 x 6.022 x 1023

There are 2 × 100/28 x 6.022 x 1023 = 43.01 x 1023 atoms.

For NH3

100 g of NH3 equals 100/17 moles.

Molecule count is equal to 100/17 x 6.022 x 1023 molecules.

Atomic number of NH3 is (1 + 3) = 4 × 100/17 x 6.022 x 1023.

10.23 x 141.69 atoms.

Thus, NH3 contains more atoms than N2, which is why.

Explanation:

The Mg atom and Mg2+ ion are separated by two electrons.

The difference between 103 moles of Mg2+ and Mg atoms is

103 moles plus two electrons

2 103 moles of electrons have a mass of 2 103 6.023 1023 9.1 10-31 kg

2×6.022 × 9.1×10–5kg

109.6004 ×10–5 kg

1.096 × 10–3kg

Explanation:

a) 103 = 1000= kilo

(b) 10–1 =1/10= 0.1= deci

(c) 10–2 =1/100 = 0.01= centi

(d) 10–6 = 0.000 001= micro

(e) 10–9 =0.000 000 001 = nano

(f) 10–12 =0.000 000 000 001 = pico

Explanation:

(a) 5.84 × 10–3 mg = 5.84 ×10–9 kg

(b) 58.34 g =5.834 ×10–2 kg

(c) 0.584g =5.84 ×10–4 kg

(d) 5.873×10-21g=5.873 ×10–24 kg

Explanation:

Chlorophyll/Sunlight = C6 H12 O6 + 6O2 = 6CO2 + 6 H2 O

Needs 1 mole of glucose 6 moles of liquid 180 grammes of glucose require 618 grammes of water. 180 g of water are required to dissolve 1 g of glucose.

For every 18 g of glucose, 10.8 g of water (108/180) would be required.

Utilized water volume equals mass times density

= 10.8 g/ 1g cm-3

= 10.8 cm3