Question 511 Mark
Write the full form of $IUPAC.$
Answer
View full question & answer→International Union of Pure and Applied Chemistry
Questions · Page 2 of 5
Do as directed; [1 M ]
Question 521 Mark
Calculate the molar mass of the following substances:
Phosphorus molecule, $\mathrm{P}_4$ (atomic mass of phosphorus $=31$ ).
Phosphorus molecule, $\mathrm{P}_4$ (atomic mass of phosphorus $=31$ ).
Answer
View full question & answer→Molar mass of phosphorus molecule, $\mathrm{P} 4=4 \rightarrow 31=124 \mathrm{~g}$.
Question 531 Mark
Define the following terms. Molecule.
Answer
View full question & answer→A molecule is two or more atoms connected by chemical bonds, which form the smallest unit of a substance that retains the composition and properties of that substance. Molecules form the basis of chemistry. Molecules are noted with the element symbol and a subscript with the number of atoms.
Question 541 Mark
What are the building blocks of matter?
Answer
View full question & answer→Atoms are called the building block of matter. Atom: An atom is composed of positive, negative, and neutral subatomic particles.
Question 551 Mark
Write the formula of the following compound: Sodium phosphate.
Answer
View full question & answer→The formula of sodium phosphate is $Na _3 PO_ 4 .$
Question 561 Mark
What name is given to the amount of substance containing $6.022 \times 10^{23}$ particles (atoms, molecules or ions) of a substance?
Answer
View full question & answer→The name given to the amount of substance containing $6.022 \times 1023$ particles is 1 mole.
Question 571 Mark
Name the scientist who gave atomic theory of matter.
Answer
View full question & answer→John Dalton was the one who gave the atomic theory of matter. The atomic theory of matter: Matter is made up of small particles called atoms that cannot be divided.
Question 581 Mark
Find the ratio by mass of the combining elements in the following compounds.
$\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}$
$\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}$
Answer
View full question & answer→Hence the ratio by mass of the combining elements is $\mathrm{C} 2 \mathrm{H} 5 \mathrm{OH}=12: 3: 8$.
Question 591 Mark
Which unit is used to measure the atomic radius$?$ Convert it into metre.
Answer
View full question & answer→Fermi unit is used to measure the atomic radius. $1$ Fermi $=10^{-15} \mathrm{~m}$.
Question 601 Mark
Find the ratio by mass of the combining elements in the following compounds. $\mathrm{H}_2 \mathrm{SO}_4$
Answer
View full question & answer→The ratio by mass of the combining elements in $\mathrm{H}_2 \mathrm{SO}_4$ is $1:16:32.$
Question 611 Mark
Calculate: The number of moles of Sulphur ($S _8$) present in 16g of solid sulphur.
Answer
View full question & answer→Step 1: Calculate the number of moles.
- The number of moles can be calculated by using the formula:
Number of moles $=\frac{\text { Given mass }}{\text { Molar mass }}$
- According to the question, the given mass is $16 g$ and the molecular mass can be calculated as:
Molecular mass of $S _8=32 \times 8=256 g mol ^{-1}$
- Thus, the number of moles of $S _8$ are $\frac{16 g }{256 g mol ^{-1}}=0.0625$ moles
Step 2: Calculate the number of molecules.
- We know that one mole of any substance contains $6.023 \times 10^{23}$ molecules Thus, the number of molecules in any material may be calculated by multiplying the number of moles by Avogadro's number, which is $6.023 \times 10^{23}$.
- We can state:
Number of molecules $=$ number of moles $\times 6.023 \times 10^{23}$
- Thus, the number of molecules in $16 g$ of $S_8$ are $=0.0625 \times 6.023 \times 10^{23}=3.764 \times 10^{22}$
So, the number of molecules in $16 g$ of $S_8$ are $3.764 \times 10^{22}$
- The number of moles can be calculated by using the formula:
Number of moles $=\frac{\text { Given mass }}{\text { Molar mass }}$
- According to the question, the given mass is $16 g$ and the molecular mass can be calculated as:
Molecular mass of $S _8=32 \times 8=256 g mol ^{-1}$
- Thus, the number of moles of $S _8$ are $\frac{16 g }{256 g mol ^{-1}}=0.0625$ moles
Step 2: Calculate the number of molecules.
- We know that one mole of any substance contains $6.023 \times 10^{23}$ molecules Thus, the number of molecules in any material may be calculated by multiplying the number of moles by Avogadro's number, which is $6.023 \times 10^{23}$.
- We can state:
Number of molecules $=$ number of moles $\times 6.023 \times 10^{23}$
- Thus, the number of molecules in $16 g$ of $S_8$ are $=0.0625 \times 6.023 \times 10^{23}=3.764 \times 10^{22}$
So, the number of molecules in $16 g$ of $S_8$ are $3.764 \times 10^{22}$
Question 621 Mark
Write the chemical formula using criss-cross method: Magnesium bicarbonate.
Answer
View full question & answer→The Criss cross method is shown below: The atomic number of magnesium is $12,$ and the valency of magnesium is two, while the valency of bicarbonate is one. To satisfy the valency of the magnesium atom, it requires two bicarbonates. Therefore, the correct formula of magnesium bicarbonate is $M g ( H C O _3 ) _2 .$
Question 631 Mark
Define the following terms.
Avogadro's number.
Avogadro's number.
Answer
View full question & answer→ The number of units in one mole of any substance is called Avogadro's number or Avogadro's constant.
Question 641 Mark
What do we call those particles which are formed: By the gain of electrons by atoms?
Answer
View full question & answer→Anions: The atom gains an electron to form "negative" charged ions. These ions are then called anions.
Question 651 Mark
Convert $12g$ of oxygen gas into mole, if atomic mass of oxygen is $16u.$
Answer
View full question & answer→Number of moles in $12g\ O2 =$ Given mass/ Molar mass $= 12/32 = 0.375$ mole.
Question 661 Mark
Convert $12g$ of oxygen gas into moles.
Answer
View full question & answer→Number of moles in $12 \mathrm{~g} \mathrm{O}_2=$ Given mass/ Molar mass $=12 / 32=0.375$ mole.
Question 671 Mark
Write down the names of $Q$ compounds represented by the following formulae: $\mathrm{CaCO}_3$.
Answer
View full question & answer→$\mathrm{CaCO}_3$ represents the compound calcium carbonate.
Question 681 Mark
In a chemical compound calcium sulphate:
Write the chemical formula of compound formed when positive ion is replaced by sodium ion.
Write the chemical formula of compound formed when positive ion is replaced by sodium ion.
Answer
View full question & answer→In a chemical compound calcium sulphate write the chemical formula of compound formed when positive ion is replaced by Sodium ion. The compound formed is Sodium Sulphate and formula is $\mathrm{Na}_2 \mathrm{SO}_2$.
Question 691 Mark
Why is it not possible to see an atom with naked eyes?
Answer
View full question & answer→The size of an atom is so small that it is not possible to see it with naked eyes. Also, the atom of an element does not exist independently.
Question 701 Mark
Write down the formulae for the following compounds: Calcium oxide.
Answer
View full question & answer→The chemical formula of calcium oxide is $C a O.$
Question 711 Mark
Write the chemical formulae of the following:
Magnesium chloride.
Magnesium chloride.
Answer
View full question & answer→The chemical formula for Magnesium chloride is $\mathrm{MgCl}_2$.
Question 721 Mark
Define ‘formula mass’ of a compound.
Answer
View full question & answer→The formula mass of a substance is defined as the sum of the atomic masses of constituent atoms in an ionic compound. This is generally used for ionic compounds which do not contain discrete molecules, but ions as their constituent units.
Question 731 Mark
Name the compound represented by formula $\mathrm{K}_2 \mathrm{SO}_4$
Answer
View full question & answer→Potassium Sulfate
Question 741 Mark
What is the mass of. $10$ moles of sodium sulphite $(Na_2SO_3)?$
Answer
View full question & answer→The mass of $10$ moles of sodium sulphite $(Na_2SO_3)$ is: $10×[2×23+32+3×16]g=10×126 g=1260 g.$
Question 751 Mark
Write the molecular formulae for the following compounds.
Mercury (II) chloride.
Mercury (II) chloride.
Answer
View full question & answer→It consists of one mercury (II) cation $\left(\mathrm{Hg}^{+2}\right)$ and two chloride anions $\left(\mathrm{Cl}^{-1}\right)$. The molecular or chemical formula of Mercury (II) chloride is $\mathrm{HgCl}_2$.
Question 761 Mark
State whether the following statement is true or false:
The symbol of element cobalt is $CO.$
The symbol of element cobalt is $CO.$
Answer
View full question & answer→False, The symbol of cobalt is $Co.$
Question 771 Mark
An element has a valency of $3.$ write the simplest formula for sulphide of the element.
Answer
View full question & answer→The given valency of element $= 3.$ Let's assume the symbol of an element be $X.$ And, sulfide ion carries the charge of 2$-,$ hence by criss-cross, we get the formula is $X_2S_3.$
Question 781 Mark
Calculate:
the number of molecules of $0.25$ moles of $\mathrm{NH}_3$,
the number of molecules of $0.25$ moles of $\mathrm{NH}_3$,
Answer
View full question & answer→$1.5 \times 10^{23}$ molecules
Question 791 Mark
An element $X$ has a valency $1:$
Write the chemical formula of its chloride.
Write the chemical formula of its chloride.
Answer
View full question & answer→the formula of the compound which formed when $X$ reacts with chlorine is $XCl.$
Question 801 Mark
An element $X$ of valency $3$ combines with another element $Y$ of valency $2.$ What will be the formula of the compound formed$?$
Answer
View full question & answer→Formula for the compound formed between $X$ and $Y$ can be worked out by crossing the valencies of the constituent elements. Therefore, formula of the compound is $X_2 Y_3$.
Question 811 Mark
- In what form does oxygen gas occur in nature$?$
- In what form do noble gases occur in nature$?$
Answer
View full question & answer→$(a)$ The oxygen is found in diatomic nature in a free atmosphere.
$(b)$ Noble gases occur as monoatomic gases in nature.
$(b)$ Noble gases occur as monoatomic gases in nature.
Question 821 Mark
Give the names of the elements present in the following compounds.
Baking powder.
Answer
View full question & answer→ The elements present in baking powder are sodium, hydrogen, carbon, and oxygen.
Question 831 Mark
Name the scientist who gave: Law of constant proportions.
Answer
View full question & answer→Law of constant proportions was given by Joseph Proust in $1799.$
Question 841 Mark
Calculate the molecular mass of ethanoic acid, $\mathrm{CH}_3 \mathrm{COOH}$.
(Atomic masses: $\mathrm{C}=12 \mathrm{u} ; \mathrm{H}=1 \mathrm{u} ; \mathrm{O}=16 \mathrm{u}$ )
(Atomic masses: $\mathrm{C}=12 \mathrm{u} ; \mathrm{H}=1 \mathrm{u} ; \mathrm{O}=16 \mathrm{u}$ )
Answer
View full question & answer→The molecular mass of $\mathrm{CH}_3 \mathrm{COOH}$ is $60.052 g/mol$.
Question 851 Mark
Give one major drawback of Dalton’s atomic theory of matter.
Answer
View full question & answer→According to Dalton's atomic theory, matter is indivisible, i.e., which cannot be divided. But now it is known that under special circumstances, atoms can be divided into still smaller particles called electrons, protons and neutrons. This was the major drawback of Dalton's atomic theory of matter.
Question 861 Mark
Write the atomicity of the following: $\mathrm{Na}_2 \mathrm{SO}_4$
Answer
View full question & answer→The Atomicity of $\mathrm{Na}_2 \mathrm{SO}_4$ is $7$.
Question 871 Mark
Define atomic mass of an element.
Answer
View full question & answer→The atomic mass is a weighted average of all of the isotopes of that element, in which the mass of each isotope is multiplied by the abundance of that particular isotope.
Question 881 Mark
Why is it not possible to see an atom with the unaided eyes?
Answer
View full question & answer→Atoms are very tiny particles that are measured in nanometres. Hence they cannot be seen with the naked eye, but can only be seen under a microscope.
Question 891 Mark
In a chemical compound calcium sulphate: dentify the two ions.
Answer
View full question & answer→Calcium sulphate is a compound formed by the combination of calcium ion and sulphate ion. Calcium ion carry two positive charge $(Ca_2+)$ whereas sulphate ion carry two negative ion($SO_2−4)$, both combine to form a neutral compound $CaSO_4.$
Question 901 Mark
Calculate the molar mass of the following compound:
$\mathrm{H}_3 \mathrm{PO}_4$
$\mathrm{H}_3 \mathrm{PO}_4$
Answer
View full question & answer→$3 (H) + (P) + 4(O) = 3 (1) + 31 + 4(16) = 3 + 31 + 64 = 98. -$ So, the molecular weight or molar mass of the phosphoric acid is $98.$
Question 911 Mark
What is the name of a particle which contains $10$ electrons, $11$ protons and $12$ neutrons$?$
Answer
View full question & answer→The particle that contains $10$ electrons, $11$ protons and $12$ neutrons is a positively-charged sodium ion $(Na+).$
Question 921 Mark
Calculate the number of moles in $112g$ of iron.
Answer
View full question & answer→Since $56\ g$ of iron $= 1\ mol.$ Therefore, $112\ g$ of iron$= 1/ 56 ×112\ mol = 2\ mol.$
Question 931 Mark
Write the molecular formulae for the following compounds. Copper (II) bromide.
Question 941 Mark
Calculate the molar mass of the following substances: Sulphur molecule, $S_8$.
Answer
View full question & answer→Molar mass of sulphur molecule, $S_8=8 \times 32=256 \mathrm{~g}$
Question 951 Mark
State the number of atoms present in the following chemical species,$\text{CO}^{2-}_3$
Answer
View full question & answer→$4(1$ atom of carbon and 3 atom of oxygen$.)$
Question 961 Mark
Write the chemical formulae and names of the compounds formed by the following ions:
$\mathrm{Cr}^{3+}$ and $\mathrm{SO}_4{}^{2-}$
$\mathrm{Cr}^{3+}$ and $\mathrm{SO}_4{}^{2-}$
Answer
View full question & answer→$\mathrm{Cr}^{3+}$ and $\mathrm{SO}_4{}^{2-}: \mathrm{Cr}_2\left(\mathrm{SO}_4\right)_3=$ Chromium sulphate.
Question 971 Mark
Write down the formulae of. sodium oxide.
Answer
View full question & answer→Sodium oxide
Question 981 Mark
Write the atomicity of the following:
$S_8$
$S_8$
Answer
View full question & answer→$S_8$: The atomicity of $S_8$ is $8$ because it contains 8 atoms of Sulphur.
Question 991 Mark
Which of the following symbols of elements are incorrect$?$ Give their correct symbols. Aluminium $AL$
Answer
View full question & answer→Aluminium $AL$ is incorrect symbol. Its correct symbol is $Al.$
Question 1001 Mark
What is the mass of: $0.2$ mole of oxygen atoms$?$
Answer
View full question & answer→$1$ mole of oxygen atoms $= 16\ gm.\ 0.2$ moles of oxygen atoms $= 16 \times 0.2 = 3.2\ gm.$