Questions and Answers
What characterizes the chemical reaction between quicklime and water?
Which of the following reactions is endothermic?
When zinc granules react with dilute sulfuric acid, the temperature of the reaction mixture:
What is formed when quicklime reacts with water?
Signup and view all the answers
Which chemical reaction involves the release of hydrogen gas?
Signup and view all the answers
Which reaction mixture becomes very cold due to heat absorption?
Signup and view all the answers
Why does the temperature rise when burning carbon in air?
Signup and view all the answers
Which of the following reactions involves the formation of barium chloride, ammonia, and water?
Signup and view all the answers
What is the immediate observable change when potassium iodide solution is added to lead nitrate solution in a test tube?
Signup and view all the answers
What happens when citric acid reacts with potassium permanganate solution?
Signup and view all the answers
What is observed when a chemical reaction produces heat energy?
Signup and view all the answers
What is the typical effect on temperature when a chemical reaction absorbs heat energy?
Signup and view all the answers
Which of the following pairs correctly describes the type of change and the observable effect in the reaction between lead nitrate and potassium iodide?
Signup and view all the answers
Which of the following reactions is characterized by the evolution of hydrogen gas?
Signup and view all the answers
What type of change is observed when two substances form a precipitate?
Signup and view all the answers
Which example involves the reaction of an acid with a metal?
Signup and view all the answers
Which of the following is NOT an observable characteristic of a chemical reaction?
Signup and view all the answers
Which reaction is characterized by the evolution of carbon dioxide gas?
Signup and view all the answers
What is observed when potassium iodide is added to a solution of lead nitrate?
Signup and view all the answers
What indicates the presence of a chemical reaction when zinc reacts with dilute sulfuric acid besides the evolution of hydrogen gas?
Signup and view all the answers
Which of the following statements is true regarding the formation of a precipitate?
Signup and view all the answers
Which of the following statements correctly defines a balanced chemical equation?
Signup and view all the answers
Why is the given equation: H2 + O2 → H2O, considered unbalanced?
Signup and view all the answers
In the balanced chemical equation 'Zn + H2SO4 → ZnSO4 + H2', how many atoms of oxygen are present in the products?
Signup and view all the answers
Which law is being followed when the atoms in the reactants are equal to the atoms in the products in a chemical reaction?
Signup and view all the answers
Which pair of reactants and their corresponding products correctly exemplify a balanced chemical equation?
Signup and view all the answers
Considering the equation H2 + O2 → H2O, how can it be balanced?
Signup and view all the answers
Which of the following is a characteristic of a balanced chemical equation?
Signup and view all the answers
What does the equation 'Zn + H2SO4 → ZnSO4 + H2' demonstrate about the reaction?
Signup and view all the answers
What is a characteristic of the combustion reaction of candle wax?
Signup and view all the answers
Which substances are the products of the reaction between zinc and sulphuric acid?
Signup and view all the answers
In the reaction between potassium iodide and lead nitrate solution, which characteristics are observed?
Signup and view all the answers
According to the balanced chemical equation for the reaction of zinc and sulphuric acid, how many hydrogen atoms are found in the reactants?
Signup and view all the answers
What is represented by the arrow (→) in a chemical equation?
Signup and view all the answers
Which of the following reactions shows both a change in temperature and evolution of gas?
Signup and view all the answers
Which equation correctly represents the symbolic form of the reaction between zinc and sulphuric acid?
Signup and view all the answers
Which characteristic is NOT associated with the reaction between zinc and dilute sulphuric acid?
Signup and view all the answers
What is the symbol and formula of sulphuric acid?
Signup and view all the answers
What is one way a chemical reaction can be represented?
Signup and view all the answers
What is the key indicator for identifying an exothermic reaction in a chemical equation?
Signup and view all the answers
Which of the following is a correct representation of an endothermic reaction?
Signup and view all the answers
Which reaction indicates heat absorption and hence an endothermic reaction?
Signup and view all the answers
What is common among all combustion reactions?
Signup and view all the answers
Which scenario describes an exothermic process?
Signup and view all the answers
In which of the following conditions would you typically write '+ Heat' on the reactants' side?
Signup and view all the answers
In the equation $H_2 + O_2 \rightarrow H_2O$, what is the main reason that it is initially unbalanced?
Signup and view all the answers
After balancing the number of oxygen atoms in the equation $H_2 + O_2 \rightarrow 2H_2O$, what imbalance occurs?
Signup and view all the answers
Which step is required to balance the hydrogen atoms in the equation $H_2 + O_2 \rightarrow 2H_2O$?
Signup and view all the answers
Which of the following is the correctly balanced equation for hydrogen burning in oxygen to form water?
Signup and view all the answers
What is the definition of balancing an equation in chemistry?
Signup and view all the answers
In which process is the hit and trial method mainly employed?
Signup and view all the answers
Which of the following combination represents the reactants in the equation $2H_2 + O_2 \rightarrow 2H_2O$?
Signup and view all the answers
In the final balanced equation $2H_2 + O_2 \rightarrow 2H_2O$, what are the coefficients of $H_2$ and $O_2$, respectively?
Signup and view all the answers
What does the symbol (aq) represent in a chemical equation?
Signup and view all the answers
Which of the following equations represents the reaction of calcium hydroxide with carbon dioxide?
Signup and view all the answers
What is indicated by the symbol (s) in a chemical equation?
Signup and view all the answers
Which of the following enhances the informativeness of a chemical equation?
Signup and view all the answers
What product is formed as a precipitate when calcium hydroxide reacts with carbon dioxide?
Signup and view all the answers
Which state symbol is correctly matched with its meaning?
Signup and view all the answers
How many hydrogen atoms are present in the products of the balanced equation for the reaction between hydrogen and chlorine?
Signup and view all the answers
What does the chemical equation 'Zn (s) + H₂SO₄ (aq) → ZnSO₄ (aq) + H₂ (g)' illustrate?
Signup and view all the answers
What does the symbol (l) indicate in a chemical equation?
Signup and view all the answers
What are the state symbols for the reactants and products in the balanced equation of iron reacting with steam?
Signup and view all the answers
Which equation shows the formation of a precipitate?
Signup and view all the answers
In the balanced equation of the reaction between hydrogen and nitrogen to form ammonia, how many molecules of ammonia are produced?
Signup and view all the answers
For a reaction to be in a balanced state, what must be equal on both sides?
Signup and view all the answers
Which of the following correctly balances the equation for hydrogen reacting with chlorine?
Signup and view all the answers
What is the formula of iron (II, III) oxide?
Signup and view all the answers
In the reaction between hydrogen and nitrogen to form ammonia, what is the stoichiometric coefficient of hydrogen in the balanced equation?
Signup and view all the answers
How many iron atoms are present on both sides of the balanced equation for the reaction between iron and steam?
Signup and view all the answers
When balancing the equation for the reaction of hydrogen with nitrogen to form ammonia, which molecule is adjusted last?
Signup and view all the answers
What type of reaction is the decomposition of calcium carbonate?
Signup and view all the answers
Which conditions are necessary for the photosynthesis reaction to occur?
Signup and view all the answers
Which of the following equations correctly represents the decomposition of potassium chlorate using a catalyst?
Signup and view all the answers
Which of the following is an endothermic reaction?
Signup and view all the answers
What pressure and temperature conditions are required for the production of methanol from carbon monoxide and hydrogen?
Signup and view all the answers
What is the catalyst used in the production of methanol from carbon monoxide and hydrogen?
Signup and view all the answers
Which gas is produced alongside potassium chloride when potassium chlorate decomposes?
Signup and view all the answers
What is indicated by the delta (Δ) sign over the arrow in a chemical equation?
Signup and view all the answers
Study Notes
Characteristics of Chemical Reactions
- A chemical reaction involves the conversion of reactants into products.
- Characteristics of chemical reactions include:
- Evolution of a gas
- Formation of a precipitate
- Change in color
- Change in temperature
- Change in state
Evolution of a Gas
- Some chemical reactions are characterized by the evolution of a gas.
- Examples:
- Reaction between zinc and dilute sulfuric acid to produce hydrogen gas
- Reaction between sodium carbonate and dilute hydrochloric acid to produce carbon dioxide gas
Formation of a Precipitate
- A precipitate is a solid product that separates out from a solution during a chemical reaction.
- Examples:
- Reaction between potassium iodide solution and lead nitrate solution to form a yellow precipitate of lead iodide
Change in Colour
- Some chemical reactions are characterized by a change in colour.
- Example:
- Reaction between citric acid and potassium permanganate, where the purple colour of the potassium permanganate solution disappears
Change in Temperature
- Chemical reactions can produce or absorb heat energy.
- Examples:
- Reaction between quicklime and water, where heat is produced and the temperature rises
- Reaction between barium hydroxide and ammonium chloride, where heat is absorbed and the temperature falls
Change in State
- Some chemical reactions are characterized by a change in state.
- Example:
- Combustion reaction of wax, where the physical state changes from solid to liquid and gas
Chemical Equations
- A chemical equation is a method of representing a chemical reaction using symbols and formulae of the substances involved.
- The reactants are written on the left-hand side of the equation, and the products are written on the right-hand side.
- The arrow sign (→) points from the reactants to the products.
Balanced and Unbalanced Chemical Equations
- A balanced chemical equation has an equal number of atoms of each element on both sides of the equation.
- An unbalanced chemical equation does not have an equal number of atoms of each element on both sides of the equation.
- Examples:
- Balanced equation: Zn + H2SO4 → ZnSO4 + H2
- Unbalanced equation: H2 + O2 → H2O
Balancing of Chemical Equations
- The process of making the number of atoms of each element equal on both sides of the equation is called balancing.
- Methods of balancing include:
- Hit and trial method
- Counting the number of atoms of each element on both sides of the equation
Making Equations More Informative
- Chemical equations can be made more informative by:
- Indicating the physical states of the reactants and products
- Indicating the heat changes taking place in the reaction
- Indicating the conditions under which the reaction takes place
Physical States of Reactants and Products
- The physical states of reactants and products can be indicated using symbols such as (s) for solid, (l) for liquid, (aq) for aqueous solution, and (g) for gas.
Heat Changes in an Equation
- Reactions can be classified as exothermic or endothermic based on the heat changes involved.
- Exothermic reactions evolve heat, while endothermic reactions absorb heat.
- Examples:
- Exothermic reaction: C(s) + O2(g) → CO2(g) + Heat
- Endothermic reaction: N2(g) + O2(g) + Heat → 2NO(g)
Conditions Under Which the Reaction Takes Place
-
The conditions under which the reaction takes place can be indicated in the equation using symbols such as Δ for heat, and the symbol or formula of the catalyst.
-
Examples:
-
2KClO2(s) Δ MnO2 → 2KCl(s) + 3O2(g)### Chemical Equations and Reactions
-
The production of methanol involves the reaction: CO (g) + 2H2 (g) → CH3OH (l) at 300 atm and 300°C.
Photosynthesis
- Green plants produce food through photosynthesis, combining carbon dioxide with water in the presence of sunlight and chlorophyll to form glucose and oxygen.
Balanced Chemical Equations
- A balanced equation has an equal number of atoms of each type in the reactants and products.
- Example: 3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4H2 (g)
Writing Balanced Equations
- Start with a word equation and replace the words with chemical formulas.
- Example: Hydrogen + Chlorine → Hydrogen chloride becomes H2 + Cl2 → HCl
- Balance the equation by multiplying the formulas of the reactants or products to get an equal number of atoms on both sides.
- Example: H2 + Cl2 → HCl becomes H2 + Cl2 → 2HCl
Sample Problems
- Hydrogen gas combines with chlorine to form hydrogen chloride: H2 (g) + Cl2 (g) → 2HCl (g)
- Hydrogen gas combines with nitrogen to form ammonia: 3H2 + N2 → 2NH3
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about the characteristics of chemical reactions, including the evolution of a gas, formation of a precipitate, change in color, change in temperature, and change in state.