Chemical Reactions and Equations
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Questions and Answers

What is a key observation that indicates a chemical reaction has occurred when burning magnesium ribbon?

  • It smells like burnt rubber.
  • It produces a colored flame.
  • It changes into a white powder. (correct)
  • It makes a popping sound.

Which of the following scenarios exemplifies a chemical change?

  • Fermentation of grapes. (correct)
  • Boiling water to steam.
  • Dissolving sugar in water.
  • Melting ice to form water.

What product is formed when magnesium burns in the presence of oxygen?

  • Magnesium dioxide.
  • Magnesium hydroxide.
  • Magnesium chloride.
  • Magnesium oxide. (correct)

In the context of chemical reactions, what distinguishes a chemical change from a physical change?

<p>Chemical changes alter the identity of the substances involved. (D)</p> Signup and view all the answers

When food is cooked, which type of change typically occurs?

<p>Both physical and chemical changes. (D)</p> Signup and view all the answers

Which of the following activities requires caution due to the involvement of acids?

<p>Mixing zinc with hydrochloric acid. (D)</p> Signup and view all the answers

What term describes the change in the identity of the initial substance during a reaction?

<p>Chemical alteration. (D)</p> Signup and view all the answers

Which of the following best describes a common misconception about chemical reactions?

<p>Chemical reactions occur without energy changes. (D)</p> Signup and view all the answers

Which of the following observations indicates that a chemical reaction has occurred?

<p>Change in color (A), Change in temperature (D)</p> Signup and view all the answers

In the word-equation 'Magnesium + Oxygen → Magnesium oxide', what role does magnesium play?

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

What does the arrow in a word-equation signify?

<p>Transformation from reactants to products (D)</p> Signup and view all the answers

Which of the following is NOT considered a chemical change?

<p>Mixing salt in water (A)</p> Signup and view all the answers

What is formed when magnesium reacts with oxygen?

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

Which statement accurately describes reactants in a chemical reaction?

<p>They undergo a chemical change to form products. (A)</p> Signup and view all the answers

What can be inferred if there is an evolution of gas during a reaction?

<p>A chemical reaction has occurred (D)</p> Signup and view all the answers

Which chemical equation correctly represents the combustion of magnesium in oxygen?

<p>Mg + O2 → MgO (B)</p> Signup and view all the answers

What happens to the blue color of copper sulphate solution after immersing iron nails in it?

<p>It fades. (D)</p> Signup and view all the answers

What is the color change observed in the iron nails after being immersed in copper sulphate solution?

<p>They become brownish. (C)</p> Signup and view all the answers

What type of reaction is demonstrated when iron displaces copper from copper sulphate solution?

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

Which of the following is a product of the reaction between iron and copper sulphate solution?

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

Which metals can displace copper from its compounds based on their reactivity?

<p>Zinc and lead (D)</p> Signup and view all the answers

What happens to the concentration of copper ions in the solution after the reaction?

<p>It decreases. (B)</p> Signup and view all the answers

Which type of reaction involves the combination of two or more substances to form a new single substance?

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

In the equation Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s), what role does iron play?

<p>It is a reactant that is oxidized. (D)</p> Signup and view all the answers

After the experiment, how can the difference in the blue color be quantitatively assessed?

<p>By comparing the intensity of the color in test tubes A and B. (B)</p> Signup and view all the answers

What is a key characteristic of decomposition reactions?

<p>They consume energy. (A)</p> Signup and view all the answers

In the reaction 2PbO(s) + C(s) → 2Pb(s) + CO2(g), which statement regarding oxidation and reduction is correct?

<p>Carbon is getting oxidized. (C)</p> Signup and view all the answers

Which type of reaction results in the production of hydrogen gas and iron chloride when dilute hydrochloric acid is added to iron filings?

<p>Single displacement reaction (C)</p> Signup and view all the answers

What defines an exothermic reaction?

<p>It releases energy along with the products. (A)</p> Signup and view all the answers

Which process is described as the loss of oxygen or gain of hydrogen?

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

What is the purpose of balancing a chemical equation?

<p>To maintain the ratio of reactants to products (C)</p> Signup and view all the answers

In a double displacement reaction, what primarily occurs?

<p>Two different atoms or groups of atoms exchange places. (B)</p> Signup and view all the answers

What are the products formed when hydrogen gas reacts with chlorine gas?

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

What type of reaction is represented by the equation: Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)?

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

Which equation properly represents a double displacement reaction?

<p>BaCl2 + H2SO4 → BaSO4 + HCl (C)</p> Signup and view all the answers

What occurs during a precipitation reaction?

<p>A solid is produced from two liquids. (D)</p> Signup and view all the answers

Which of the following reactions is considered an exothermic reaction?

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

In barium chloride reacting with potassium sulphate, what is the end product?

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

What is the outcome when potassium metal reacts with water?

<p>Potassium hydroxide and hydrogen gas (C)</p> Signup and view all the answers

Which of the following best describes oxidation?

<p>Gain of oxygen (B)</p> Signup and view all the answers

How many oxygen atoms are present in the reactants of the unbalanced equation Fe + H2O → Fe3O4 + H2?

<p>1 (C)</p> Signup and view all the answers

What is the first step in balancing the chemical equation Fe + H2O → Fe3O4 + H2?

<p>Draw boxes around each formula. (C)</p> Signup and view all the answers

Which element is selected first when balancing the equation based on the number of atoms in Fe3O4?

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

What should be used to balance the oxygen atoms in the equation Fe + H2O → Fe3O4 + H2?

<p>4 H2O (A)</p> Signup and view all the answers

What is the total number of hydrogen atoms in the products after balancing the equation Fe + H2O → Fe3O4 + H2?

<p>4 (B)</p> Signup and view all the answers

In the balanced equation, Fe + 4 H2O → Fe3O4 + 4 H2, what is the total number of iron atoms on the products side?

<p>3 (B)</p> Signup and view all the answers

What is the importance of not altering the formulae of the compounds while balancing?

<p>It maintains the identity and properties of the substances. (A)</p> Signup and view all the answers

After completing the balancing process, how many total atoms are on each side of the equation Fe + 4 H2O → Fe3O4 + 4 H2?

<p>10 (D)</p> Signup and view all the answers

Flashcards

Chemical Change

A process where the original substance loses its properties and is transformed into a new substance.

Chemical Reaction

A process where the nature and identity of a substance change.

Magnesium Ribbon

A thin strip of magnesium metal.

Lead Nitrate

A chemical compound.

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Magnesium Oxide

A white powder formed when magnesium burns in air.

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Zinc Granules

Small pieces of zinc metal.

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Dilute Acid

A solution with a low concentration of acid.

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Chemical Equation

A representation of a chemical reaction using chemical formulas and symbols.

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Chemical Reaction

A process where one or more substances change into new substances.

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Reactants

Substances that undergo change in a chemical reaction.

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Products

The new substances formed during a chemical reaction.

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Word Equation

A representation of a chemical reaction using the names of the reactants and products.

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Chemical Equation

A symbolic representation of a chemical reaction using chemical formulas.

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Change in state

A physical change in a substance from one state (solid, liquid, gas) to another in a reaction

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Change in color

A visible change in the color of a substance during a chemical reaction.

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Evolution of a gas

Production of a gas as a product of a chemical reaction.

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Balanced Chemical Equation

A chemical equation where the number of atoms of each element is equal on both sides of the equation.

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Chemical Equation Balancing

Process of adjusting coefficients in a chemical equation to make the number of atoms of each element the same on both sides.

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Coefficients in Equations

Numbers placed in front of chemical formulas to adjust the number of molecules/atoms in a chemical equation.

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Unbalanced Equation (Reactants and Products)

A chemical equation where the number of atoms of at least one element is not the same on both sides.

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Balancing Oxygen Atoms

Adjusting the coefficients to match the number of oxygen atoms on both sides of a chemical equation.

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Cannot Change Formulas

The chemical formulas of compounds in a chemical equation cannot be altered during balancing; only the coefficients can be changed.

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Balancing with Coefficients

Adjusting the number of molecules using coefficients to balance the chemical equation.

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Element Balancing

Adjusting the number of molecules of different elements (e.g., Fe, H, O) using coefficients to match quantities on both sides of the chemical equation, so each element has a balanced number of atom.

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Displacement Reaction

A chemical reaction where a more reactive element takes the place of a less reactive element in a compound.

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Iron Displacing Copper

Iron is more reactive than copper, and in a reaction with copper sulfate, iron replaces copper in the compound.

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Copper Sulfate Solution

A solution containing copper sulfate, appearing in a blue colour.

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More Reactive Element

An element that has a stronger tendency to undergo chemical reactions or displacement.

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Iron Nail Color Change

In a displacement reaction with copper sulfate, iron nails turn brownish as copper settles on the nail.

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Copper Displacement

Copper is removed from its compound (copper sulfate) by a more reactive element (e.g., iron).

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Chemical Equation (Fe + CuSO4)

Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s); A representation of the reaction between iron(s) and copper sulphate(aq) giving iron sulphate(aq) and copper(s).

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Intensity Change (CuSO4)

The color of a copper sulfate solution fades as it loses copper during a displacement reaction.

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Balanced Chemical Equation

A chemical equation with equal numbers of each type of atom on both sides of the equation.

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Combination Reaction

Two or more substances combine to form a single new substance.

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Decomposition Reaction

A single substance breaks down into two or more substances.

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Oxidation

Gain of oxygen or loss of hydrogen.

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Reduction

Loss of oxygen or gain of hydrogen.

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Displacement Reaction

One element replaces another element in a compound.

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Double Displacement Reaction

Two different ions in two different compounds exchange places.

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What is a chemical reaction?

Chemical Reaction: the process where a substance or substances are changed into a new substance or substances. Chemical equations describe these reactions.

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Exothermic Reaction

A chemical reaction that releases heat to the surroundings.

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Endothermic Reaction

A chemical reaction that absorbs heat from the surroundings.

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Decomposition Reaction

A reaction where a single reactant breaks down into two or more products.

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Combination Reaction

A reaction where two or more reactants combine to form a single product.

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Displacement Reaction

A reaction where one element replaces another element in a compound.

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Double Displacement Reaction

A reaction where two compounds exchange ions to form two new compounds.

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Precipitation Reaction

A reaction where an insoluble solid (precipitate) is formed when two solutions are mixed.

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Oxidation

A reaction where a substance gains oxygen or loses electrons.

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Study Notes

Chemical Reactions and Equations

  • Chemical reactions involve changes in the nature and identity of substances.
  • Chemical reactions involve the breaking and forming of bonds between atoms.
  • Signs that a chemical reaction has occurred include a change in state, color, temperature, or the evolution of a gas.
  • A chemical reaction can be represented by a word equation, showing reactants and products with words.
  • Chemical reactions can also be represented using chemical formulas, called a chemical equation.
  • Chemical equations must be balanced to satisfy the law of conservation of mass, ensuring the same number of each atom type on both sides of the equation.
  • A word equation shows reactants and products.
  • Reactants are the substances that undergo a chemical change.
  • Products are the new substances formed.
  • The arrow in an equation points to the product.
  • The number of each atom is equal on both sides of the equation.

Activity 1.1

  • Students clean a magnesium ribbon and burn it using a spirit lamp.
  • Observe the visible changes.
  • Record observations of ash and color changes.

Activity 1.2

  • Add potassium iodide to lead nitrate solution.
  • Observe any changes in color or formation of precipitation.

Activity 1.3

  • Zinc granules are added to dilute hydrochloric acid or sulfuric acid.
  • Observe for any reaction occurring.
  • Check the temperature change.

Types of Chemical Reactions:

  • Combination Reactions: A single product forms from two or more reactants.
    • Ex: CaO(s) + Hâ‚‚O(l) → Ca(OH)â‚‚(aq) (Heat released)
  • Decomposition Reactions: A single reactant breaks down into two or more products by supplied energy.
    • Ex: 2FeSOâ‚„(s) → Feâ‚‚O₃(s) + SOâ‚‚(g) + SO₃(g) (Heat supplied in the reaction)
  • Displacement Reactions: One element displaces another element in a compound.
    • Ex: 2Fe(s) + CuSOâ‚„(aq) → FeSOâ‚„(aq) + Cu(s)
  • Double Displacement Reactions: Ions from two different compounds exchange to form new compounds.
    • Ex: Naâ‚‚SOâ‚„(aq) + BaClâ‚‚(aq) → BaSOâ‚„(s) + 2NaCl(aq)
  • Oxidation-Reduction (Redox) Reactions: A reaction where substances gain or lose electrons. (one substance is oxidized, the other reduced)
    • Ex: 2CuO(s) + Hâ‚‚(s) → 2Cu(s) + Hâ‚‚O(g)

Physical States of Matter

  • (s) - solid
  • (l) - liquid
  • (g) - gas
  • (aq) - aqueous (dissolved in water)

Balancing Chemical Equations

  • Count the number of atoms of each element on both sides of the equation.
  • Adjust coefficients (numbers in front of formulas) to make the number of each atom type equal on both sides.

Examples

  • Magnesium + Oxygen → Magnesium Oxide
  • 2Mg(s) + Oâ‚‚(g) --> 2MgO(s)

Other key concepts

  • Corrosion: The gradual deterioration of metals due to chemical reactions with substances in the environment.
  • Rancidity: The unpleasant odor and taste change in fats and oils due to oxidation reactions from air contact.

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Description

Explore the fundamental concepts of chemical reactions and equations in this engaging quiz. Learn about the nature of substances, signs of chemical reactions, and how to represent these reactions with word and chemical equations. Perfect for students looking to solidify their understanding of chemical processes.

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