Basic Concepts Of Chemistry Flashcards
(166 cards)
1
Q
What is chemistry?
A
The science of molecules and their transformations
It studies the preparation, properties, structure, and reactions of material substances.
2
Q
What are the three states of matter?
A
Solid, Liquid, Gas
Each state has distinct characteristics based on particle arrangement.
3
Q
How can matter be classified at the macroscopic level?
A
As a mixture or pure substance
A pure substance has the same chemical nature for all its particles.
4
Q
What is a pure substance?
A
A substance where all constituent particles are the same in chemical nature.
5
Q
What is a mixture?
A
A combination of two or more pure substances present in any ratio.
6
Q
What happens to a solid when heated?
A
It usually changes to a liquid.
7
Q
What is the definition of matter?
A
Anything which has mass and occupies space.
8
Q
What are the characteristics of solids?
A
Definite volume and definite shape.
9
Q
What are the characteristics of liquids?
A
Definite volume but no definite shape; they take the shape of their container.
10
Q
What are the characteristics of gases?
A
No definite volume or shape; they completely occupy the space in their container.
11
Q
What is the significance of atomic mass?
A
It is significant in determining the molecular mass and formula mass of compounds.
12
Q
What are the SI base units?
A
Fundamental units used for measuring physical quantities.
13
Q
What is the mole in chemistry?
A
A unit that quantifies the amount of substance.
14
Q
What is molar mass?
A
The mass of one mole of a substance.
15
Q
What is stoichiometry?
A
The calculation of reactants and products in chemical reactions.
16
Q
Fill in the blank: Chemistry is often intertwined with __________.
A
other branches of science.
17
Q
True or False: Chemistry contributes to environmental protection.
A
True.
18
Q
What is the role of chemistry in the pharmaceutical industry?
A
Isolation of life-saving drugs and synthesis of new drugs.
19
Q
What is the ‘Philosopher’s Stone’ in the context of the history of chemistry?
A
A mythical substance believed to convert baser metals into gold.
20
Q
What did Acharya Kanda contribute to chemistry?
A
The concept of atomic theory and the idea of indivisible particles called ‘Paramãnu’.
21
Q
What is the historical significance of alchemy in chemistry?
A
Alchemy was an early form of chemistry focused on transformation of materials.
22
Q
What is the importance of empirical and molecular formulas?
A
They represent the composition of compounds and can be derived from experimental data.
23
Q
What is the purpose of using scientific notation in chemistry?
A
To express large or small numbers conveniently.
24
Q
What are significant figures?
A
Digits in a number that contribute to its precision.
25
What does precision refer to in measurements?
The consistency of repeated measurements.
26
What does accuracy refer to in measurements?
The closeness of a measurement to the true value.
27
What is the historical significance of the Charaka Samhita?
It describes ancient Indian medical practices and the reduction of particle size in metals.
28
Fill in the blank: The process of ________ was well-known to ancient Indians.
fermentation.
29
What is the role of chemistry in agriculture?
Production of fertilizers, pesticides, and insecticides.
30
What are some examples of materials produced through chemistry?
Fertilizers, drugs, polymers, dyes, metals, and alloys.
31
What is the classification of matter at the macroscopic level?
Matter can be classified as mixture or pure substance
32
What defines a pure substance?
All constituent particles of a substance are the same in chemical nature
33
What is a mixture?
A mixture contains particles of two or more pure substances which may be present in any ratio
34
How can mixtures be categorized?
Mixtures can be homogeneous or heterogeneous
35
What characterizes a homogeneous mixture?
Components completely mix with each other and are uniformly distributed
36
Give examples of homogeneous mixtures.
* Sugar solution
* Air
37
What characterizes a heterogeneous mixture?
Composition is not uniform throughout and different components may be visible
38
Give examples of heterogeneous mixtures.
* Mixture of salt and sugar
* Grains and pulses with dirt
39
How can components of a mixture be separated?
By using physical methods such as hand-picking, filtration, crystallisation, distillation
40
What are the characteristics of pure substances?
Constituent particles have fixed composition and cannot be separated by physical methods
41
What are examples of pure substances?
* Copper
* Silver
* Gold
* Water
* Glucose
42
How are pure substances classified?
Into elements and compounds
43
What defines an element?
Particles consist of only one type of atom
44
Give examples of elements.
* Sodium
* Copper
* Silver
* Hydrogen
* Oxygen
45
What is a compound?
A molecule formed when two or more atoms of different elements combine in a definite ratio
46
How can compounds be separated?
Only by chemical methods
47
Give examples of compounds.
* Water
* Ammonia
* Carbon dioxide
* Sugar
48
What is the relationship between the properties of a compound and its constituent elements?
The properties of a compound are different from those of its constituent elements
49
What are physical properties?
Properties that can be measured or observed without changing the identity of the substance
50
What are examples of physical properties?
* Colour
* Odour
* Melting point
* Boiling point
* Density
51
What are chemical properties?
Properties that require a chemical change to be observed
52
What is the SI unit of length?
Metre (m)
53
What is the SI unit of mass?
Kilogram (kg)
54
What is the SI unit of time?
Second (s)
55
What defines the International System of Units (SI)?
Established by the 11th General Conference on Weights and Measures (CGPM)
56
How many base units are there in the SI system?
Seven base units
57
What is the SI unit of electric current?
Ampere (A)
58
What is the SI unit of thermodynamic temperature?
Kelvin (K)
59
What is the SI unit of amount of substance?
Mole (mol)
60
What is the SI unit of luminous intensity?
Candela (cd)
61
What is the formula for density?
Density = Mass / Volume
62
What is the common unit for measuring volume in chemistry?
Litre (L)
63
What is the relationship between mass and weight?
Mass is constant, while weight varies due to gravity
64
What is temperature measured in?
°C (Celsius), °F (Fahrenheit), K (Kelvin)
65
What is the relationship between Celsius and Kelvin?
K = °C + 273.15
66
True or False: Negative temperatures are possible in the Kelvin scale.
False
67
What is the relationship between Kelvin and Celsius scales?
K = °C + 273.15
68
Are negative temperatures possible in the Kelvin scale?
No, negative temperatures are not possible in the Kelvin scale.
69
What is the reference standard for mass since 1889?
The kilogram, defined as the mass of a platinum-iridium cylinder.
70
Why was platinum-iridium chosen as the standard for mass?
Because it is highly resistant to chemical attack and its mass does not change over time.
71
What is the current definition of a metre as of 1983?
The length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second.
72
What is scientific notation?
A way to express numbers in the form N × 10^n, where N is between 1 and 9.999... and n is an exponent.
73
How is the number 232.508 expressed in scientific notation?
2.32508 × 10^2
74
How is the number 0.00016 expressed in scientific notation?
1.6 × 10–4
75
What is the rule for multiplication in scientific notation?
Multiply the coefficients and add the exponents.
76
What is the rule for addition in scientific notation?
Make the exponents the same and then add the coefficients.
77
What are significant figures?
Meaningful digits known with certainty plus one estimated digit.
78
What is the significance of the digit after the decimal in a measurement?
It indicates uncertainty in the measurement.
79
How many significant figures are in the number 285 cm?
Three significant figures.
80
Are leading zeros significant in measurements?
No, leading zeros are not significant.
81
What is precision in measurements?
Closeness of various measurements for the same quantity.
82
What is accuracy in measurements?
Agreement of a particular value to the true value.
83
What happens to the result in addition and subtraction of significant figures?
The result cannot have more digits to the right of the decimal point than either of the original numbers.
84
In multiplication and division, how is the result reported?
With no more significant figures than the measurement with the fewest significant figures.
85
What is dimensional analysis?
A method used to convert units from one system to another.
86
How many seconds are in 2 days?
172,800 seconds.
87
What law states that mass is conserved in chemical reactions?
Law of Conservation of Mass.
88
Who proposed the Law of Conservation of Mass?
Antoine Lavoisier.
89
What is the Law of Conservation of Mass?
In all physical and chemical changes, there is no net change in mass. Matter can neither be created nor destroyed.
## Footnote
Proposed by Antoine Lavoisier in 1789.
90
Who proposed the Law of Definite Proportions?
Joseph Proust.
## Footnote
This law states that a given compound always contains exactly the same proportion of elements by weight.
91
What does the Law of Multiple Proportions state?
If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in the ratio of small whole numbers.
## Footnote
Proposed by Dalton in 1803.
92
What is Gay Lussac's Law of Gaseous Volumes?
When gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume at the same temperature and pressure.
## Footnote
Proposed by Gay Lussac in 1808.
93
What is Avogadro's Law?
Equal volumes of all gases at the same temperature and pressure contain equal number of molecules.
## Footnote
Proposed by Amedeo Avogadro in 1811.
94
What are the key points of Dalton's Atomic Theory?
* Matter consists of indivisible atoms
* All atoms of a given element have identical properties
* Atoms of different elements differ in mass
* Compounds are formed when atoms of different elements combine in a fixed ratio
* Chemical reactions involve reorganisation of atoms
## Footnote
Published in 'A New System of Chemical Philosophy' in 1808.
95
What is the atomic mass based on?
The atomic mass is based on Carbon-12 as the standard, assigned a mass of exactly 12 amu.
## Footnote
This system was agreed upon in 1961.
96
What is the average atomic mass?
It is computed by taking into account the existence of isotopes and their relative abundance.
## Footnote
Example: Average atomic mass of carbon is 12.011 u.
97
How is molecular mass calculated?
Molecular mass is the sum of atomic masses of the elements present in a molecule, obtained by multiplying the atomic mass of each element by the number of its atoms.
## Footnote
Example: Molecular mass of methane (CH4) = 16.043 u.
98
What is the formula mass?
The formula mass is calculated using the atomic masses of the constituent ions in compounds that do not contain discrete molecules.
## Footnote
Example: Formula mass of sodium chloride (NaCl) = 58.5 u.
99
What is a mole?
The mole is the SI unit of the amount of substance, containing exactly 6.02214076 × 10²³ elementary entities.
## Footnote
This number is known as Avogadro's constant.
100
What is the molar mass?
The mass of one mole of a substance in grams, numerically equal to its atomic/molecular/formula mass in u.
## Footnote
Example: Molar mass of water = 18.02 g/mol.
101
How is percentage composition of an element in a compound calculated?
Mass % of an element = (mass of that element in the compound × 100) / molar mass of the compound.
## Footnote
Example: For water (H2O), mass % of hydrogen = 11.18% and mass % of oxygen = 88.79%.
102
Fill in the blank: The Law of Definite Proportions is sometimes referred to as the _______.
Law of Definite Composition.
103
True or False: Dalton's Atomic Theory could explain the laws of gaseous volumes.
False.
## Footnote
Dalton's theory could not explain the laws of gaseous volumes.
104
What is the mass % of hydrogen in water?
11.18%
## Footnote
Mass % of hydrogen = (mass of hydrogen / molar mass of water) × 100 = (2.016 g / 18.02 g) × 100
105
What is the mass % of oxygen in water?
88.79%
## Footnote
Mass % of oxygen = (mass of oxygen / molar mass of water) × 100 = (16.00 g / 18.02 g) × 100
106
What is the molecular formula of ethanol?
C2H5OH
107
What is the molar mass of ethanol?
46.068 g
108
What is the mass percent of carbon in ethanol?
52.14%
## Footnote
Mass % of carbon = (mass of carbon / molar mass of ethanol) × 100 = (24.02 g / 46.068 g) × 100
109
What is the mass percent of hydrogen in ethanol?
13.13%
## Footnote
Mass % of hydrogen = (mass of hydrogen / molar mass of ethanol) × 100 = (6.048 g / 46.068 g) × 100
110
What is the mass percent of oxygen in ethanol?
34.73%
## Footnote
Mass % of oxygen = (mass of oxygen / molar mass of ethanol) × 100 = (16.00 g / 46.068 g) × 100
111
What is an empirical formula?
Represents the simplest whole number ratio of various atoms present in a compound.
112
What does a molecular formula represent?
Shows the exact number of different types of atoms present in a molecule of a compound.
113
How can empirical formulas be determined?
If the mass percent of various elements is known.
114
What is the empirical formula for a compound containing 4.07% hydrogen, 24.27% carbon, and 71.65% chlorine?
CH2Cl
115
What is the molar mass of the compound in the empirical formula example?
98.96 g
116
What is stoichiometry?
The calculation of masses (and sometimes volumes) of reactants and products in a chemical reaction.
117
What are reactants and products in a chemical reaction?
Reactants are substances that undergo a chemical change, while products are the substances formed as a result.
118
What is a limiting reagent?
The reactant that is consumed first in a chemical reaction, limiting the amount of product formed.
119
What is mass percent (w/w %)?
The mass of the solute divided by the total mass of the solution, multiplied by 100.
120
What is molarity?
The number of moles of solute per liter of solution.
121
What is the balanced equation for the combustion of methane?
CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g)
122
How many moles of CH4 are needed to produce 22 g of CO2?
0.5 mol
123
What is the molar mass of water?
18 g/mol
124
How much NH3 is formed from the reaction of 50 kg of N2 and 10 kg of H2?
56.1 kg NH3
125
What is mole fraction?
The ratio of the number of moles of a particular component to the total number of moles of the solution.
126
What is the significance of stoichiometric coefficients in a balanced equation?
They represent the number of molecules (and moles) participating in the reaction.
127
Is the equation P4(s) + O2(g) → P4O10(s) balanced?
No, it is unbalanced.
128
What is the empirical formula mass for CH2Cl?
49.48 g
129
What does the law of conservation of mass state about balanced chemical equations?
They have the same number of atoms of each element on both sides.
130
Fill in the blank: The mass percent is calculated using the formula _____ = (mass of solute / total mass of solution) × 100.
mass percent
131
True or False: The coefficients in a balanced equation can be changed to balance an equation.
False
132
What does 1 M NaOH mean?
1 mol of NaOH present in 1 litre of the solution.
133
How many moles of NaOH are required for a 0.2 M solution?
0.2 moles of NaOH dissolved in 1 litre of solution.
134
What volume of 1 M NaOH solution contains 0.2 moles of NaOH?
200 mL of 1 M NaOH.
135
What formula is used to calculate dilution?
M1 × V1 = M2 × V2.
136
In the dilution formula, what does M1 represent?
Initial molarity (0.2 M in this case).
137
What is molality defined as?
Number of moles of solute present in 1 kg of solvent.
138
How is molality denoted?
It is denoted by 'm'.
139
What is the molality of a 3 M NaCl solution with a density of 1.25 g/mL?
2.79 m.
140
What is the significance of a stock solution?
A solution of higher concentration used for dilution.
141
How does temperature affect molality?
Molality does not change with temperature.
142
What are the states of matter?
* Solid * Liquid * Gas
143
How can matter be classified?
* Elements * Compounds * Mixtures
144
What is an element?
Contains particles of only one type, either atoms or molecules.
145
What defines a compound?
Atoms of two or more elements combine in a fixed ratio.
146
What is the SI unit system?
International System of Units.
147
What does significant figures represent?
The precision of measurements.
148
What is Avogadro's constant?
6.022 × 10^23.
149
What does a balanced chemical equation provide?
Molar ratios and number of particles in a reaction.
150
What is stoichiometry?
Quantitative study of reactants and products in a chemical reaction.
151
What is the average atomic mass based on?
Natural abundance of different isotopes.
152
What is the formula for calculating molecular mass?
Sum of the atomic masses of different atoms in a molecule.
153
What is the molar mass of sodium acetate (CH3COONa)?
82.0245 g/mol.
154
What is the concentration of a solution expressed in?
* Mass per cent * Mole fraction * Molarity * Molality
155
What is the significance of the Law of Conservation of Mass?
Mass is conserved in chemical reactions.
156
Identify the limiting reagent in a reaction: 300 atoms of A + 200 molecules of B.
To be determined based on the stoichiometry.
157
What is the empirical formula of a compound with 69.9% iron and 30.1% dioxygen?
To be calculated based on mass percent.
158
What is the mass per cent of nitric acid in a sample with 69% concentration?
To be determined based on density.
159
How many significant figures are in the number 0.0025?
Two significant figures.
160
Calculate the volume of methanol needed for making 2.5 L of a 0.25 M solution if its density is 0.793 kg/L.
To be calculated based on molarity and density.
161
What is the pressure in pascal if the mass of air at sea level is 1034 g/cm²?
To be calculated based on force per unit area.
162
What is the SI unit of mass?
Kilogram (kg).
163
Match the following prefixes with their multiples: micro, deca, mega, giga, femto.
* micro: 10^-6 * deca: 10^1 * mega: 10^6 * giga: 10^9 * femto: 10^-15
164
What is the concentration of sugar (C12H22O11) in mol L–1 if 20 g are dissolved in 2 L?
To be calculated based on molarity.
165
How is the limiting reagent identified in a reaction?
By comparing the mole ratios of reactants.
166
What is the mass of CaCO3 required to react with 25 mL of 0.75 M HCl?
To be calculated based on stoichiometry.
