Chemistry Chapter 1 Quiz

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Questions and Answers

Which of the following is a diatomic molecule?

  • O2 (correct)
  • Ar
  • O3
  • He

Metals typically have a simple structure consisting of a definite number of atoms bonded together.

False (B)

What term is used to describe the number of atoms that make up a molecule?

atomicity

A molecule of ozone consists of ______ atoms of oxygen.

<p>three</p> Signup and view all the answers

Match the compound with the correct mass ratio of elements:

<p>Water (H2O) = Hydrogen:Oxygen = 1:8 Ammonia (NH3) = Nitrogen:Hydrogen = 14:3 Carbon dioxide (CO2) = Carbon:Oxygen = 3:8</p> Signup and view all the answers

What is the unit used to measure atomic radius?

<p>Nanometers (nm) (C)</p> Signup and view all the answers

Dalton's symbols for elements represented only the element and not a specific quantity of it.

<p>False (B)</p> Signup and view all the answers

What organization approves the names of elements, symbols, and units?

<p>IUPAC</p> Signup and view all the answers

The name of the element copper was taken from the place name of ______.

<p>Cyprus</p> Signup and view all the answers

Match the size with the example.

<p>$10^{-10}$ m = Atom of hydrogen $10^{-9}$ m = Molecule of water $10^{-8}$ m = Molecule of haemoglobin $10^{-3}$ m = Ant</p> Signup and view all the answers

According to Dalton's atomic theory, which characteristic is unique to each element?

<p>Atomic mass (D)</p> Signup and view all the answers

The names of all elements are derived from the name of the place where they were found.

<p>False (B)</p> Signup and view all the answers

Berzilius suggested that the symbols of elements should be made from:

<p>One or two letters of the name of the element (A)</p> Signup and view all the answers

What is the formula for ammonium sulfate?

<p>(NH4)2SO4 (D)</p> Signup and view all the answers

The molecular mass of $H_2O$ is 16 u.

<p>False (B)</p> Signup and view all the answers

What is the molecular mass of $HNO_3$?

<p>63 u</p> Signup and view all the answers

The formula unit mass of a substance is the sum of the atomic masses of all _______ in a formula unit of a compound.

<p>atoms</p> Signup and view all the answers

Which of the following compounds' constituent particles are ions?

<p>Sodium chloride (NaCl) (B)</p> Signup and view all the answers

Molecular mass and formula unit mass are calculated using different methods.

<p>False (B)</p> Signup and view all the answers

Match the chemical formula with the correct compound name:

<p>$Na_2O$ = Sodium oxide $AlCl_3$ = Aluminium chloride $Na_2S$ = Sodium sulfide $Mg(OH)_2$ = Magnesium hydroxide</p> Signup and view all the answers

According to the reaction $2H_2 + O_2 → 2H_2O$, how many molecules of hydrogen are required to react with one molecule of oxygen?

<p>2 (A)</p> Signup and view all the answers

What type of compound is formed when two different elements combine?

<p>Binary compound (A)</p> Signup and view all the answers

When writing chemical formulas, the charges on the ions are always indicated in the final formula.

<p>False (B)</p> Signup and view all the answers

What is the formula of a compound formed from one calcium ion (Ca$^{2+}$) and one oxygen ion (O$^{2-}$)?

<p>CaO</p> Signup and view all the answers

In the compound $Mg(OH)_2$, the number of hydroxide ions ($OH^−$) is indicated by writing the number of ions outside the ______.

<p>bracket</p> Signup and view all the answers

Match the formula with it's compound name:

<p>Al2(SO4)3 = Aluminum sulfate CaCl2 = Calcium chloride K2SO4 = Potassium sulfate KNO3 = Potassium nitrate CaCO3 = Calcium carbonate</p> Signup and view all the answers

Which of the following represents the correct formula for magnesium chloride?

<p>MgCl2 (C)</p> Signup and view all the answers

According to the rules for writing chemical formulae, if only one polyatomic ion is present in a compound, brackets are required around the ion's formula.

<p>False (B)</p> Signup and view all the answers

What is the process called where valencies are exchanged to determine the formula of a compound?

<p>Crossover</p> Signup and view all the answers

What is the relationship between atomic mass expressed in 'u' and molar mass expressed in 'g' for a substance?

<p>Only the units change, the numerical value remains the same. (B)</p> Signup and view all the answers

1 mole of hydrogen atoms always contains a different number of atoms than 1 mole of oxygen atoms.

<p>False (B)</p> Signup and view all the answers

What quantity relates the number of particles to the amount in moles?

<p>Avogadro Number</p> Signup and view all the answers

The mass of $6.022 \times 10^{23}$ atoms of hydrogen is approximately 1 ______.

<p>gram</p> Signup and view all the answers

Match the following amounts of substance to the corresponding number of moles of Helium:

<p>52 g of He = 13 moles 4 g of He = 1 mole 8 g of He = 2 moles 2 g of He = 0.5 moles</p> Signup and view all the answers

What mass of oxygen gas (O₂) is present in 12 g of oxygen gas?

<p>12 g (A)</p> Signup and view all the answers

0.2 moles of oxygen atoms (O) has a mass greater than 20 g.

<p>False (B)</p> Signup and view all the answers

What is the mass of 0.5 mole of water molecules (H₂O)?

<p>9 g</p> Signup and view all the answers

The formula for sodium sulphate is Na₂______.

<p>SO₄</p> Signup and view all the answers

Which of the following formulas is correct for sodium phosphate?

<p>Na₃PO₄ (A)</p> Signup and view all the answers

The mass of an ion is significantly different from the mass of an atom of the same element.

<p>False (B)</p> Signup and view all the answers

What is the molar mass of carbon dioxide (CO₂)?

<p>44 g/mol</p> Signup and view all the answers

Match the following ions with their respective valencies:

<p>Na⁺ = +1 SO₄²⁻ = -2 PO₄³⁻ = -3</p> Signup and view all the answers

Flashcards

Molecules of Elements

Molecules consisting of the same type of atoms.

Diatomic Molecule

A molecule made up of two atoms of the same element.

Ozone

A molecule of oxygen consisting of three atoms (O3).

Atomicity

The number of atoms that constitute a molecule.

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Ratio by Mass

The mass ratio of elements combined in a compound.

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Dalton's Symbols

John Dalton was the first to use symbols to represent elements, indicating both the element and a specific quantity.

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Atomic Radius

The size of an atom, typically measured in nanometers (nm), where 1 nm = 1/1,000,000,000 m.

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Measurement of Atoms

Atoms are measured in nanometers, with 10^-10 m representing the size of a hydrogen atom.

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Relative Sizes of Molecules

Relative sizes of different structures, with atoms being around 10^-10 m and grains of sand around 10^-4 m.

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Element Naming Origins

Names of elements often originated from locations or colors, such as copper from Cyprus and gold from 'yellow'.

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IUPAC

The International Union of Pure and Applied Chemistry establishes official names and symbols for chemical elements.

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Dalton's Atomic Mass Concept

Dalton proposed that every element has a unique atomic mass, an idea central to atomic theory.

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Atomic Mass Significance

Atomic mass is a characteristic property of an element, distinguishing it from others in terms of quantity.

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Avogadro's Number

The number of particles in one mole, approximately 6.022 × 10²³.

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Mole

A unit measuring the amount of substance, equivalent to Avogadro's number of molecules or atoms.

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Molar Mass

The mass of one mole of a substance, expressed in grams per mole (g/mol).

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Molecular Mass of Water

The molecular mass of H₂O is 18 u, meaning 18 grams equal one mole of water.

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Atomic Mass

The mass of a single atom, usually measured in atomic mass units (u).

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Magnesium Chloride Formula

The chemical formula for magnesium chloride is MgCl2.

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Binary Compounds

Simplest compounds made from two different elements.

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Valency

The combining power of an element, usually measured by the number of hydrogen atoms it can combine with.

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Crossover Method

A technique to combine atomic valencies to balance charges in a compound.

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Hydrogen Chloride Formula

The chemical formula for hydrogen chloride is HCl.

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Sodium Nitrate Formula

The chemical formula for sodium nitrate is NaNO3.

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Aluminium Oxide Formula

The chemical formula for aluminium oxide is Al2O3.

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Calcium Oxide Formula

The chemical formula for calcium oxide is CaO.

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Molecular mass of HNO3

Atomic mass calculation: 1 + 14 + 3 × 16 = 63 u

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Formula unit mass

Sum of atomic masses of all atoms in a formula unit of a compound.

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Sodium chloride (NaCl)

An example of a compound whose mass is calculated as a formula unit.

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Formula unit of CaCl2

Calculated by adding the atomic masses of Ca and Cl: 1 × 40.1 + 2 × 35.5.

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Reaction of hydrogen and oxygen

2H2 + O2 → 2H2O represents water formation.

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Atomic mass of oxygen

The atomic mass of oxygen is 16 u.

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Hydrogen atomic mass

The atomic mass of hydrogen is approximately 1 u.

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Mass of oxygen atoms (0.2 mole)

Calculated mass of 0.2 mole of oxygen atoms is 3.2 g (O atomic mass = 16 g/mol).

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Mass of water molecules (0.5 mole)

Calculated mass of 0.5 mole of water is 9 g (H2O molar mass = 18 g/mol).

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Molecules in 16 g of sulphur (S8)

Number of S8 molecules in 16 g of sulphur is 0.5 moles (Molar mass of S8 = 256 g/mol).

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Aluminium ions in 0.051 g Al2O3

There are approximately 0.001 moles of Al ions in 0.051 g of aluminium oxide (Al2O3).

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Symbol of sodium (Na)

Na is the chemical symbol for sodium, an alkali metal.

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Valency of sulphate (SO4 2-)

The valency of sulphate ion is -2.

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Formula for sodium sulphate (Na2SO4)

Sodium sulphate results from combining 2 sodium ions with 1 sulphate ion.

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Sodium phosphate formula

Formula for sodium phosphate is Na3PO4, combining sodium with phosphate.

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Study Notes

Atomic Structure and Molecular Compounds

  • Ancient Indian and Greek philosophers pondered matter's divisibility, with Maharishi Kanad proposing "Parmanu" (indivisible particles) and Pakudha Katyayama expanding on this concept.
  • Greek philosophers Democritus and Leucippus proposed "atoms" (indivisible particles).
  • By the 18th century, scientists recognized the distinction between elements and compounds, seeking to understand how and why elements combine.

Laws of Chemical Combination

  • Lavoisier's Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.

  • Proust's Law of Constant Proportions (Definite Proportions): Elements in a compound always combine in fixed proportions by mass.

Dalton's Atomic Theory

  • All matter is composed of atoms.
  • Atoms of the same element are identical in mass and properties.
  • Atoms of different elements have different masses and properties.
  • Atoms combine in simple whole-number ratios to form compounds.
  • Atoms are indivisible and indestructible in chemical reactions.

Modern Atomic Symbols

  • Dalton introduced symbols for elements.
  • Berzelius established a system using one or two letters, with the first capitalized.

Atomic Mass

  • Dalton's theory introduced atomic mass, using the mass of known elements as a relative scale.
  • A standard, carbon-12, was defined in 1961 for calculating the relative atomic mass of other elements.

Atoms and Molecules

  • Atoms are the fundamental building blocks of matter, frequently existing in combinations.
  • Molecules represent the smallest units of elements or compounds with defined properties.

Molecules of Elements and Compounds

  • Molecules of elements consist of the same atoms.
  • Molecules of compounds consist of different atoms in definite proportions.
  • Atomicity is the number of atoms in a molecule.

What is an Ion?

  • Ions are charged species (atoms or groups of atoms).
  • Anions are negatively charged.
  • Cations are positively charged.

Writing Chemical Formulae

  • Chemical formulae depict the composition of a compound.
  • Valencies (combining capacity) influence how atoms combine in compounds.
  • Writing formula rules include balancing charges/valencies and appropriate symbols for constituent elements.

Molecular Mass and Mole Concept

  • Molecular mass is the sum of atomic masses in a molecule.
  • A mole is a unit of amount of substance, containing 6.022 x 1023 particles.
  • Formula unit mass is analogous to molecular mass for ionic compounds.

Additional Concepts

  • Examples and calculations showcasing the applications of these concepts are present in the text.

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