Answer

Answer is (d) (ii) and (iv)

Explanation:

Number of moles $=\dfrac{\text{ Mass of water }}{\text{ Molar mass of water }}$

Number of moles $={360 g}$ $18 g / mol$

Number of moles $=20$

Number of molecules $=20 \times 6.022 \times 10^{23}=1.2044 \times 10^{25}$ molecules of water

Thus, option (d) is correct.

Answer

Answer is (d) Atoms aggregate in large numbers to form the matter that we can see, feel or touch

Explanation:

Atoms aggregate in large numbers to form the matter But we cannot see the matter with our naked eyes.

Answer

Answer is (b) $N _2$

Explanation:

Chemical formula of Nitrogen is $N$ but Nitrogen exist in molecule of two ions hence chemical symbol of Nitrogen is written as $N _2$.

Answer

Answer is (d) $Na$

Explanation:

Sodium word is derived from Latin word Natrium hence the chemical name of sodium is Na.

Answer

Answer is (c) 2 moles of $CaCO _3$

Explanation:

Weight of a sample in grant $=$ Number of moles $x$ Molar mass

(a) 0.2 moles of $Ci 2 H _220,=0.2 \times 342=68.4 g$

(b) 2 moles of $CO$ is $2 x 44$ is. $88 g$

(c) 2 moles of CaCO? 2 x IIMI - $200 g$ (4) 10 moles of I-120 = 10 x 18 - 1St g

Hence, option (c) is correct.

Answer

Answer is (d) $18 g$ of $CH _4$

Explanation:

Number of atoms $=$ substance $\times$ Number of atoms in the molecule/ Molar mass $\times$ NA

(a) $18 g$ of water $=18 \times 3 / 18 \times NA=3 NA$

(b) $18 g$ of oxygen $=18 \times 2 / 32 \times NA=1.12 NA$

(c) $18 g$ of $CO _2=18 \times 3 / 44 \times NA=1.23 NA$

(d) $18 g$ of $CH _4=18 \times 5 / 16 \times NA=5.63 NA$

Note: $N A=6.023 \times 10^{23}$

Answer

Answer is (c) $1 g H _2$

Note: NA $=6.023 \times 10^{23}$

Explanation:

$1 g$ of $H _2=1 / 2 \times NA=0.5 NA=0.5 \times 6.022 \times 1023=3.011 \times 1023$

Answer

Answer is (a) 2316 g $6.02310 \times$

Explanation:

Mass of one atom of oxygen $=$ Atomic mass $/ NA=16 / 6.023 \times 1023 g$

Note: $N A=6.023 \times 10^{23}$

Answer

Answer is (a) $6.68 \times 10^{23}$

Explanation:

1 mol of sucrose $(C 12 H _22 O 11)$ contains $=11 \times NA$ atoms of oxygen, where $NA=6.023 \times 10^{23}$

$0.01 mol$ of sucrose $(C 12 H _22 O 11)$ contains $=0.01 \times 11 \times NA$ atoms of oxygen

$=0.11 \times NA$ atoms of oxygen

$=18 g /(1 \times 2+16) gmol-1$

$=18 g / 18 gmol-1$

$=1 mol$

$1 mol$ of water $(H _2O)$ contains $1 \times NA$ atom of oxygen

Total number of oxygen atoms $=$

Number of oxygen atoms from sucrose + Number of oxygen atoms from water

$=0.11 NA+1.0 NA=1.11 NA$

Number of oxygen atoms in solution $=1.11 \times$ Avogadro’s number

$=1.11 \times 6.022 \times 10^{\prime 23}=6.68 \times 10^{23}$

Answer

Answer is (c) when energy is either given to, or taken out from the system

Short Answer Questions

Answer

Answer is (b) BiPO4, Its name is Bismuth Phosphate

Explanation:

Bismuth phosphate is right because Both ions are trivalent Bismuth phosphate(Bi3+- Trivalent anion. anion is an ion that is negatively charged).

Answer

Answers are

(a) Copper (II) bromide- CuBr2

(b) Aluminium (III) nitrate $=Al(NO 3) 3$

(c) Calcium (II) phosphate - Ca3(PO4)2

(d) Iron (III) sulphide - Fe2S3

(e) Mercury (II) chloride - $HgCl _2$

(f) Magnesium (II) acetate- $Mg(CH 3 COO) 2$

Answer

Answers are

$CuCl_2 / CuSO_4 / Cu_3(PO_4)^{2}$

$NaCl / Na_2 SO_4 / Na_3 PO^{4}$

$FeCl_3 / Fe_2(SO_4)^{3} / FePO_4$

Answer

a) In $CH_3 COONa-CH_3 COO$ is anion and $Na$ is cation.

b) In $NaCl-Cl$ anion $Na$ is cation

c) In $H_2$ both the ions are cations as they share electrovalent bond between them

d) In $NH_4 NO_3-NO_3$ is anion $NH_4$ is cation

Answer

(b) Hydrogen and sulphur- $H_2 S$ - Hydrogen Sulphide

(c) Nitrogen and hydrogen- $NH_3$ - Ammonia

(d) Carbon and chlorine $-CCl_4$ - Carbon Tetra chloride

(e) Sodium and oxygen - $Na_2 O$-Sodium Oxide

(f) Carbon and oxygen- $CO_2$; CO- Carbon-di-oxide; Carbon Monoxide

Answer

Cobalt CO is wrong, correct symbol is Co

Carbon c is wrong, correct symbol is $C$

Alluminium AL is wrong, correct symbol is $Al$

Helium He is the right symbol

Sodium So is wrong, correct symbol is $Na$

Answer

Answer

(a) $CO^{-2}-1+3=4$

(b) $PO^{-3}-{1}+{4}={5}$

(c) $P_2 O^{5}-2+5=7$

(d) $CO-1+1=2$

Answer

Mass of 1 mole of a substance is equal to its relative atomic or molecular mass in grams.

Mass of one mole (Avogadro Number) of neutrons $=1 g$

Mass of one neutron $=1$ / Avogadro number(NA) $g$

Mass of one molecule of water $=$ Molar mass $/ NA=18 / NA g$ calculated by multiplying the atomic weight of hydrogen (1.008) by two and adding the result to the weight for one oxygen (15.999)

Mass of one molecule of water $=$ Molar mass $/ NA=18 / NA g$

Avogadro number $(NA)=6.022 \times 1023 mol^{-} 1$

There are 8 neutrons in one atom of oxygen

Number of neutrons in oxygen= number of oxygen - Atomic number of oxygen

Oxygen’s atomic weight $=15.9994$

increases with an increase in temperature.

Therefore the mass is 16

Therefore number of neutrons $=16-8=8$

Mass of one neutron $=1$ / Avogadro number(NA) $g$

Mass of 8 neutrons $=8 /$ Avogadro number(NA) $g$

Fraction of mass of water due to neutrons $=8 / 18 g$

Answer

Solubility is the ability of a solute to get dissolved in $100 g$ solvent. Solubility of a given solute to dissolve in specific solvent depends on the temperature. With Increase in temperature solubility of liquids and solids increase. In the same way solubility of gases decreases with increase in temperature.

Ex: Sugar dissolves faster in hot water than in cold water.

Answer

a) Monoatomic are inert gases that do not combine and exist as monoatomic gases

b) Diatomic- (a) 2 - diatomic- $NO _2=1+2=3 ., HCl=1+1=2$

c) Triatomic-N2O $=2+1=3 ., NO _2=1+2=3, O 3=3$

d) Tetraatomic- $H _2O _2=2+2=4, P 4 O 10=4+10=14, P 4=4, CH _4=1+4=5$

e) Octa atomic- $C _2 H _6=2+6=8$

f) Polyatomic.

Answer

1. Heating: Upon heating sugar melts to liquid form because sucrose has a decomposition point and melting point at temperatures between 190 to 192 degrees Celsius. This will turn sugar to light brown colour. Upon heat further sugar gets charred to black colour.

Salt has a melting point of 841 degrees Celsius and 1545.8 degrees Fahrenheit. If we don’t heat it to that point nothing change is observed.

2. Electric conductivity:

If we dissolve the given substance in water we can check for electric conductivity to check whether the substance is sugar or salt. If it is salt it conducts electricity. Because salt $(NaCl)$ has positive sodium ions and negative chloride ions hence salt conducts electricity. But sugar don’t conduct electricity as sugar has only positive ions.

Answer

Number of moles $=\underline{\text{ weight }}$

atomic weight

$=\dfrac{12}{24}=0.5$ moles

Answer

(a) Molar mass of CO2 $=12+2 \times 16=12+32=44 g mol^{-1}$

5 moles of CO2 have mass $=44 \times 5=220 g$

Similarly, molar mass of $H _2O=2 x 1+16=18 g mol^{-1}$

5 moles of $H _2O$

$x 5=90 g$

It is verified that 5 moles of $CO_2$ and 5 moles of $H_2 O$ are not same.

(b) Number of moles $=w /$ atomic weight

Atomic weight of $Ca=40 amu$

Number of moles in $240 g$ Ca metal 240/ $40=6$

Number of moles in $240 g$ of Mg metal 240/24 $=10$

Atomic weight of $Mg=24 amu$

Ratio 6:10

Answer

a) $CaCO _3$

Ca: $C: O \times 3$

$40: 12: 16 \times 3$

40: $12: 48$

$10: 3: 12$

(b) $MgCl _2$

$Mg: Cl \times 2$

24: $35.5 \times 2$

24: 71

(c) $H _2SO _4$

$H \times 2: S: O \times 4$

2: $32: 16 \times 4$

$2: 32: 64$

1: $16: 32$

(d) $C 2 H 5 OH$

$C \times 2: H \times 6: O$

$12 \times 2: 1 \times 6: 16$

$24: 6: 16$

$12: 3: 8$ (e) $NH _3$

$N: H \times 3$

$14: 1 \times 3$

14: 3

(f) $Ca(OH) 2$

$Ca: O \times 2: H \times 2$

$40: 16 \times 2: 1 \times 2$

$40: 32: 2$

$20: 16: 1$

Answer

1 mole of calcium chloride $=111 g$

Therefore $222 g$ of $CaCl _2$ is equivalent to 2 moles of $CaCl _2$

Since 1 formula unit $CaCl _2$ gives 3 ions,

therefore, $1 mol$ of $CaCl _2$ will give 3 moles of ions 2 moles of $CaCl _2$ would give $3 \times 2=6$ moles of ions.

No. of ions $\quad=$ No. of moles of ions $\times$ Avogadro number

$=6 \times 6.022 \times 10^{23}$

$=36.132 \times 10^{23}$

$=3.6132 \times 10^{24}$ ions

Answer

Sodium atom and ion differ by one electron. For 100 moles each of sodium atoms and ions there would be a difference of 100 moles of electrons.

Mass of 100 moles of electrons $=5.48002 g$

Mass of 1 mole of electron $=5.48002 / 100 g$

Mass of one electron $=5.48002 / 100 \times 6.022 \times 10^{23}$

$=9.1 \times 10^{28} g$

$=9.1 \times 10^{-31} kg$

Answer

Molar mass of $HgS=$ The molar mass of $Hg+$ the molar mass of $S$

$=200.6+32=232.6 g mol^{-1}$

1 molecule of $HgS$ contains 1 atom of $Hg$

$232.6 g$ of HgS contains $200.6 g$ of $Hg$

Therefore, Mass of $Hg$ in $225 g$ of $HgS=\underline{200.6}$ X $225=194.04 g$

232.6

Answer

One mole of screws weigh $=2.475 \times 10^{24} g$

$ =2.475 \times 10^{21} kg $

Mass of the Earth / Mass of 1 mole of screws $=\underline{5.98 \times 10^{24} kg}$

$ 2. 475 \times 10^{21} $

Mass of earth is $2.4 \times 10^{3}$ times the mass of screws

$ =2.4 \times 10 $

The earth is 2400 times heavier than one mole of screws

Answer

We know,

1 mole $=6.022 \times 10^{23}$

The number of moles $=$ Given number of particles

Avogadro Number

$ n=\dfrac{2.58 \times 10^{24}}{6.022 \times 10^{23}} $

$n=4.28 mol$

Answer

a) Mass of sodium atoms carried by Krish $=(5 \times 23) g=115 g$

Atomic weight of $Na=23$

While mass of carbon atom carried by Raunak $=(5 \times 12) g=60 g$

b) Thus, Krish’s container has more number of atoms

Answer

Answer

Number of moles of stars $=1022$

$6.023 \times 1023$

$ =0.0166 \text{ moles } $

Answer

a) $103=1000=$ kilo

(b) $10-1=1 / 10=0.1=$ deci

(c) $10-2=1 / 100=0.01=$ centi

(d) $10-6=0.000001=$ micro

(e) $10-9=0.000000001=$ nano

(f) $10-12=0.000000000001=$ pico

Answer

(a) $5.84 \times 10^{-3} mg=5.84 \times 10^{-9} kg$

(b) $58.34 g=5.834 \times 10^{-2} kg$

(c) $0.584 g=5.84 \times 10^{-4} kg$

(d) $5.873 \times 10^{-21} g=5.873 \times 10^{-24} kg$

Answer

Mg2+ ion and Mg atom differ by two electrons.

103 moles of Mg2+ and Mg atoms would differ by

$10^{3} \times 2$ moles of electrons

Mass of $2 \times 10^{3}$ moles of electrons $=2 \times 103 \times 6.023 \times 1023 \times 9.1 \times 10^{-31} kg$ $2 \times 6.022 \times 9.1 \times 10^{-5} kg$

$109.6004 \times 10^{-5} kg$

$1.096 \times 10^{-3} kg$

Answer

No. of moles of atoms $=$ weight $/$ atomic weight.

For $N_2$

$100 gms$ of $N_2=100 / 2 \times 14$ moles $=100 / 28$ moles

Number of molecules $=100 / 28 \times 6.022 \times 10^{23}$

Molar mass of $N_2=2 x$ molar mass of monoatomic $N$

Molar mass of $N_2=2 \times 14.0067=28$ moles.

Number of molecules $=100 / 28 \times 6.022 \times 10^{23}$

No. of atoms $=2 \times 100 / 28 \times 6.022 \times 10^{23}=43.01 \times 10^{23}$

For $NH_3$ $100 gm$ of $NH_3=$

100/17 moles

Number of molecules

$=100 / 17 x$

$6.022 \times 10^{23}$ molecules

No. of atoms in $NH_3=(1+3)=4 \times 100 / 17 \times 6.022 \times 10^{23}=$

$141.69 \times 10^{23}$ atoms.

Therefore, $NH_3$ has more atoms than $N_2$.

Answer

$58.5 g NaCl$ contains $6.023 \times 10^{23}$ molecules

therefore $58.5 g NaCl$ contains $12.046 \times 10^{23}$ ions.

Hence, $5.85 g NaCl$ contains $\dfrac{5.85 \times 12.046 \times 10^{\underline{23}}}{58.5}$

$=1.2046 \times 10^{23}$ ions

Answer

One gram of gold sample will contain $\quad \dfrac{90}{100}=0.9 g$ of gold

Number of moles of gold=mass of gold

atomic mass of gold

$ =\dfrac{0.9}{19.7} $

$ =0.0046 $

One mole of gold contains NA atoms $=6.022 \times 10^{3}$

Therefore, 0.0046 mole of gold will contain $=0.0046 \times 6.022$

$ =2.77 \times 10^{21} $

Answer

While forming some compounds, atoms gain or lose electrons, and form electrically charged particles called ions. Compounds that are formed by the attraction of cations and anions are called as ionic compounds.

Ex. 2 $ Na+Cl _2 \to 2 Na+Cl \rightarrow 2 NaCl$ (sodium chloride- common salt.)

Sodium is a group 1 metal, thus forms a +1 charged cation. Chlorine is a non-metal, and has the ability to form a 1 charged anion.

Compounds formed due to bonding of uncharged ions are called as molecular compounds and the bonding between them is called covalent bonding. Molecular compounds are formed by sharing of electrons between the two atoms and the elements are held together by covalent bonds.

Ex: $2 C+O _2 \to 2 CO$ ( Carbon monoxide)

Answer

Mass of one mole of Aluminium atom $=\{13 \times$ mass of each electron $+13 \times$ mass of each proton $+14 \times$ mass of each neutron $\} \times$ Avogadro’s constant.

We know, if atoms convert into ions, only transfer of electrons takes place, in $Al+3$ ion, Aluminium atom loss three electrons,

So,

Mass of $Al+3=\{10 \times$ mass of each electron $+13 \times$ mass of each proton $+14 \times$ mass of each neutron $\}$ Avogadro’s constant

Now,

You see mass of aluminium atom is greater than aluminium ion by 3 electrons

Difference in mass $=$ Mass of Aluminium atom -mass of aluminium ion

$=3 \times$ mass of each electron $x$ Avogadro’s constant .

$=3 \times 9.1 \times 10^{-28} \times 6.023 \times 10^{23}$

$=27.3 \times 10^{-28} \times 6.023 \times 10^{23} g$

$=164.4 \times 10^{-5} g$

$=1.644 \times 10^{-3} g$

$=0.0016 g$

Answer

Mass of silver $=m g$

Mass of gold $=m / 100 g$

Number of atoms of silver $=$ Mass/ Atomic mass X NA

$=m / 108 NA$ Number of atoms of gold

$=m / 100 X 197$

Ratio of number of atoms of gold to silver $=Au: Ag$

$=m / 100 X 197 X NA: m / 108$ NA

$=108: 100 \times 197$

$=108: 19700=$

$1: 182.41$

Answer

$6.02 \times 10^{23}$ molecules of methane $=1$ mole

Hence $1.5 \times 10^{20}$ molecules of methane $=(1.5 \times 10^{20} \times 1) \div(6.02 \times 10^{23})$ moles

$ =2.49 \times 10^{-4} \text{ moles } $

Molar mass of Methane $(CH_4)=12+1 x 4=16 g$

Mass of methane $=$ molar mass $\times$ no. of moles $=16 \times 2.49 \times 10^{-4}=3.984 \times 10^{-3} g$ (This is the same mass as Ethane)

Ethane $(C _2 H _6)=12 \times 2+1 \times 6=30$

If $30 g$ of Ethane has $6.02 \times 10^{23}$ molecules

So $3.984 \times 10^{-3} g=(3.984 \times 10^{-3} \times 6.02 \times 10^{23}) \div 30$

$=8 \times 10^{19}$ molecules of Ethane

Answer

Answers

a) Law of conservation of mass

b) Ions c) 310

Explanation :

$3 \times$ atomic mass of $Ca+2 \times$ atomic mass of phosphorus $+8 \times$ atomic mass of oxygen) $=310$

$3 \times 40+2 \times 31+8 \times 16=120+62+128=310$ d) $Na _2 CO _3$ and $(NH_4)_2 SO_4$

Answer

Answer

(a)

b) Six : Helium (He); Neon ( Ne); Argon (Ar); Krypton (Kr); Xenon (Xe); Radon (Rn).

Answer

The formulae for the following and calculate the molecular mass for each one of them.

Answer

$6 CO _2+6 H _2$ O Chlorophyll /Sunlight $ \text{ arrow } C _6 H _{12} O _6+6 O _2$

1 mole of glucose needs 6 moles of water $180 g$ of glucose needs $(6 \times 18) g$ of water $1 g$ of glucose will need 108/ $180 g$ of water.

$18 g$ of glucose would need $(108 / 180) \times 18 g$ of water $=10.8 g$

Volume of water used $=\dfrac{\text{ Mass }}{\text{Density}}$

$=10.8 g / 1 g cm-3$

$=10.8 cm 3$