Download App

Science Question Answer (1 Marks)

Atoms and Molecules · Maharashtra Board STD 9 (MSBSHSE - Semi English Medium). 75 questions.

Questions · Page 1 of 2

Question Answer (1 Marks)

Take a timed test

50 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
Calculate the molecular mass of hydrogen bromide (HBr).
(Atomic masses: H = 1u; Br = 80u)
Answer
Molecular mass of hydrogen bromide (HBr)
= 1 × H + 1 × Br
= (1 + 80)u
= 81u
View full question & answer→
Question 21 Mark
If the valency of hydrogen is $1$ and that of nitrogen is $3$, work out the formula for ammonia.
Answer
$\ \text{Symbols}:\ \ \ \ \ \text{H}\ \ \ \ \ \ \ \ \ \text{N}\\ {\text{Valencies}}:\ +1\ \ \ \ -3$
So, chemical formula of ammonia is $NH_3$
View full question & answer→
Question 31 Mark
Work out the formulae for the following compounds:
Sodium oxide.
Answer
Sodium oxide:$\ \text{Symbols}:\ \ \ \ \ \text{Na}\ \ \ \ \ \ \ \text{O}\\ {\text{Valencies}}:\ +1\ \ \ \ -2$
Thus, the formula of sodium oxide is $Na_2O$
View full question & answer→
Question 61 Mark
Give the names and symbols of five familiar substances which you think are elements.
Answer
Elements
Symbols
Hydrogen
H
Helium
He
Lithium
Li
Beryllium
Be
Boron
B
View full question & answer→
Question 71 Mark
Name the law of chemical combination:
Which was given by Lavoisier.
Answer
The law of chemical combination proposed by Lavoisier is well known as the law of conservation of mass.
View full question & answer→
Question 91 Mark
Which particular atom of the above element is used for this purpose?
Answer
Atom with 6 neutrons and 6 protons in its nucleus so that its mass number is 12.
View full question & answer→
Question 101 Mark
What do the symbols, $H_2$, S and $O_4$​​​​​​​ mean in the formula $H_2SO_4$?
Answer
$H_2$​​​​​​​ represents two atoms of hydrogen, one atom of sulphur and four atoms of oxygen.
View full question & answer→
Question 121 Mark
Explain the difference between $2N$ and $N_2.$
Answer
$2N$ represents two separate atoms of nitrogen and $N_2$ represents one molecule of nitrogen.
View full question & answer→
Question 131 Mark
Stat the chemical symbols for the following elements:
Sodium, Potassium, Iron, Copper, Mercury, Silver.
Answer
Elements
Symbols
Sodium
Na
Potassium
K
Iron
Fe
Copper
Cu
Mercury
Hg
Silver
Ag
View full question & answer→
Question 151 Mark
Name the unit in which the radius of an atom is usually expressed.
Answer
The radius of an atom is usually expressed in nanometre (nm).
View full question & answer→
Question 171 Mark
Work out the formula for magnesium hydrogencarbonate.
Answer
$\ \text{Symbols}:\ \ \ \ \ \text{Mg}\ \ \ \ \ \ \text{HCO}_3\\ {\text{Valencies}}:\ \ +2\ \ \ \ \ \ \ -1$
Thus, the resulting compound is $Mg(HCO_3)_2$
View full question & answer→
Question 181 Mark
Write the relation between nanometer and metre.
Answer
$1 \text{ nanometre} = \frac{1}{109}\text{metre}$
or
$1 \text{ nanometre} = 10^{-9}\text{ metre}$
View full question & answer→
Question 191 Mark
Write the full form of IUPAC.
Answer
The full form of IUPAC is International Union of Pure and Applied Chemistry.
View full question & answer→
Question 211 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
A mole.
View full question & answer→
Question 221 Mark
Name the scientist who gave atomic theory of matter.
Answer
John Dalton proposed the atomic theory of matter.
View full question & answer→
Question 231 Mark
What do we call those particles which are formed:
By the gain of electrons by atoms?
Answer
Anions are formed by the gain of electrons by atoms.
View full question & answer→
Question 241 Mark
Convert 12g of oxygen gas into moles.
Answer
Given mass of oxygen = 12g
Molar mass of oxygen = 32g
No. of moles $=\frac{\text{Given mass}}{\text{Molar mass}}=\frac{12\text{g}}{32\text{g}}=0.375$
View full question & answer→
Question 261 Mark
Define ‘formula mass’ of a compound.
Answer
The formula mass of an ionic compound is the relative mass of its 'formula unit' as compared with the mass of a Carbon-12 atom taken as 12 units.
View full question & answer→
Question 271 Mark
State whether the following statement is true or false:
The symbol of element cobalt is CO.
Answer
False. The symbol for the element Cobalt is Co, as the second letter of the symbol of an element has to be in the lower case.
View full question & answer→
Question 281 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
$\ \text{Symbols}:\ \ \ \ \ \text{X}\ \ \ \ \ \ \text{ Y}\\ {\text{Valencies}}:\ \ \ \ \ 3\ \ \ \ \ \ \ 2$
Thus, the resulting compound is $X_2Y_3$
View full question & answer→
Question 291 Mark
  1. In what form does oxygen gas occur in nature?
  2. In what form do noble gases occur in nature?
Answer
  1. Oxygen gas occurs as a diatomic molecule in nature.
  2. Noble gases occur as mono atomic gases in nature.
View full question & answer→
Question 301 Mark
Name the scientist who gave:
Law of constant proportions.
Answer
Law of constant proportions was proposed by Joseph Proust.
View full question & answer→
Question 311 Mark
Calculate the molecular mass of ethanoic acid, $CH _3 COOH$.
(Atomic masses: $C =12 u ; H =1 u ; O =16 u$ )
Answer
Molecular mass of ethanoic acid $\left( CH _3 COOH \right)$
$=1 \times C+3 \times H+1 \times C+2 \times O+1 \times H$
$=12+3+12+32+1$
$=60 u$
View full question & answer→
Question 321 Mark
Give one major drawback of Dalton’s atomic theory of matter.
Answer
The major drawback of Dalton’s atomic theory is that atoms were thought to be indivisible. But, it is not true since atoms are divisible.
View full question & answer→
Question 331 Mark
Define atomic mass of an element.
Answer
The atomic mass of an element is the relative mass of its atom as compared with the mass of a carbon-12 atom taken as 12 units.
View full question & answer→
Question 341 Mark
What is the name of a particle which contains $10$ electrons, $11$ protons and $12$ neutrons?
Answer
Its $Na^+$, the sodium ion.
View full question & answer→
Question 351 Mark
Calculate the mass in grams of $0.17$ mole of hydrogen sulphide, $H _2 S$.
(Atomic masses: $H =1 u , S =32 u$ )
Answer
$1$ mole of H2S weights =$34\ g$
So, $0.17$ mole of H2S will weigh $= 34 \times 0.17g = 5.78\ g$
View full question & answer→
Question 361 Mark
How many atoms are there in exactly $12\ g$ of carbon $-12$ element? ($C = 12\ u$)
Answer
$6.022 \times 10^{23}$ atoms
View full question & answer→
Question 371 Mark
An element $X$ has a valency of $4$ whereas another element $Y$ has a valency of $1$. What will be the formula of the compound formed between $X$ and $Y$?
Answer
As the valency of element $X$ is $4$ and that of $Y$ is $1$, so the resulting formula is $XY_4$.
View full question & answer→
Question 381 Mark
Calculate the formulae masses of the following compounds:
Sodium oxide, $Na_2O$
(Given: Atomic masses: $Na = 23u; O = 16u; Al = 27u$)
Answer
Molecular mass of $Na_2O = (2 \times Na) + (1 \times O)$
$= (2 \times 23) + (1 \times 16)$
$= 62u$
View full question & answer→
Question 391 Mark
Name the elements represented by the following symbols:
Hg, Pb, Au, Ag, Sn.
Answer
Symbols
Elements
Hg
Mercury
Pb
Lead
Au
Silver
Ag
Silver
Sn
Tin
View full question & answer→
Question 401 Mark
The molecular formula of glucose is $C_6H_{12}O_6$. Calculate its molecular mass. (Atomic masses: $C = 12 u; H = 1 u; O = 16 u$)
Answer
Molecular formula of glucose =$C_6H_{12}O_6$
Molecular mass of glucose $= (6 \times C) + (12 \times H) + (6 \times O) = 72 + 12 + 96 = 180\ u$
View full question & answer→
Question 421 Mark
If the valency of carbon is $4$ and that of sulphur is $2$, work out the formula of the compound formed by the combination of carbon with sulphur. What is the name of this compound?
Answer
$\ \text{Symbols}:\ \ \ \ \ \text{C}\ \ \ \ \ \ \ \ \ \text{S}\\ {\text{Valencies}}:\ +4\ \ \ \ -2$
Name and formula of the resulting compound is Carbon disulphide, $CS_2$
View full question & answer→
Question 441 Mark
What do we call those particles which are formed:
By the loss of electrons by atoms?
Answer
Cations are formed by the loss of electrons by atoms.
View full question & answer→
Question 451 Mark
What is the mass of 0.2 mole of oxygen atoms?
Answer
Mass of 0.2 moles of oxygen atoms = 0.2 × 16 = 3.2g
View full question & answer→
Question 461 Mark
What is meant by 'a mole of carbon atoms'?
Answer
The amount of substance, whose mass in grams is numerically equal to its atomic mass, is called gram atomic mass of that substance. Gram atomic mass of oxygen is 16g.
View full question & answer→
Question 471 Mark
Work out the formula for sulphur dioxide.
(Valencies: $S = 4; O = 2$)
Answer
$\ \text{Symbols}:\ \ \ \ \ \text{S}\ \ \ \ \ \ \ \ \ \text{O}\\ {\text{Valencies}}:\ +4\ \ \ \ -2$
Chemical formula of sulphur dioxide is $SO_2$
View full question & answer→
Question 481 Mark
How many atoms are present in one gram atomic mass of a substance?
Answer
One mole of atoms $(6.002 \times 10^{23} atoms)$
View full question & answer→
Question 491 Mark
Name the scientist who gave:
Law of conservation of mass.
Answer
Law of conservation of mass was proposed by Antoine Lavoisier.
View full question & answer→
Question 501 Mark
An element X has a valency of 2. Write the simplest formula for:
oxide of the element.
Answer
Oxide of element: As valency of oxygen is -2 and that of element is +2 so, the resulting compound is XO.
View full question & answer→
Generate Paper FreeAll Atoms and Molecules topics
Question Answer (1 Marks) - Science STD 9 Questions - Vidyadip