Do you know the meaning of the term chemical reaction? Well, we will define it for you in a simpler manner. A chemical reaction is a change a substance undergoes to form a new one with different chemical properties. So, in short, substances react to form new substances called products.
For instance, when water evaporates and becomes vapor, this is a chemical reaction. So, the water we had, becomes vapor but now with a different chemical identity.
So, in this article, we will discuss types of chemical reactions, examples of chemical reactions, and our chemical reactions answer key.
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Chemical reactions always occur everywhere around us. For instance, if you check outside, you will notice rusted iron sheets or metals. Therefore, it's best to understand how to identify a chemical reaction.
A chemical reaction has the following characteristics;
An example of a chemical reaction is respiration, where we inhale oxygen that reacts with glucose to give out carbon dioxide(gas), water, and energy.
Let's look at these examples to understand the features of chemical reactions
Zn +2HCL =ZnCl2 +H2
Pb(NO3)2 +2KI =Pbl2 +2KNO3
BaCl2 +Na2SO4 = BaSO4 +NaCl
NH3g+ HCLg = NH4 CLs
There are several types of chemical reactions that occur in our environment. These reactions include;
NB: Precipitation and neutralization reactions are double replacements as they result in a completely new compound.
Chemical reactions occur when the starting materials known as reactants differ from the products. As a result, the products may differ in the state, color, and more. When reactions occur, they involve the movement of electrons that forms and breaks chemical bonds.
That's why you find that it's easy to break chemical bonds in some reactions, while in others, it's hard. Like in exothermic reactions that release heat, they break chemical bonds easily and thus release energy (in the form of heat) to the surrounding.
Let's discuss the different types of chemical reactions.
A reaction happens when one or more compounds combine to form a complex compound. An example of this reaction is when hydrogen gas reacts with oxygen to form water.
2H2g +O2 g = 2H2O l
Another illustration of a combination reaction occurs when oxygen reacts with an element, resulting in an oxide. Metals and non-metals react with oxygen, forming an oxide. For example, when you burn magnesium, it reacts with oxygen, producing magnesium oxide. The magnesium powder product is white.
2Mg s +O2 g = 2MgO s
This reaction occurs when aqueous solutions of anions (negatively charged ions) and cations (positively charged ions) react to form an insoluble precipitate. As a result, the products have insoluble solids (precipitate) and the remaining liquid called supernate.
Again, double replacement still means when positive and negative ions in two ionic compounds trade for places to form two new compounds.
For instance, when AB + CD = AD+ CB. A and C are positive ions, while Band D is negative. So, in double replacement, A (positively charged) combines with D (negatively charged) and C with B, exchanging places to form new products. An example of this reaction is when you add a few drops of lead(II) nitrate to a potassium iodide solution. The results are lead (II) iodide which is a yellow precipitate.
This reaction involves the breakdown of a compound into two or simpler substances. The formula of decomposition is as follows;
AB = A+B
For decomposition reactions to occur, they require energy to break down the bonds, either light, heat, or electricity. A simple example of a decomposition reaction involves binary compounds: composed of two elements. Decomposition can be both endothermic and exothermic depending on the compounds involved.
H2CO3 = H2O + CO2
2H2O = 2H2 + O2
O3 + hv = O2 = O
This reaction occurs when a single element replaces a similar element in a compound. It's still referred to as a single displacement reaction or substitution. A simple formula of the reaction includes;
A + BC = AC + B – in this case, element A, a metal, replace element B, a metal in the compound. Therefore, more reactive metals replace less reactive metals, while reactive non-metals replace less reactive non-metals.
An example is the reaction of Tin chloride and zinc. In this reaction, zinc replaces tin to form zinc chloride and tin as a single element.
SnCl2 =+ Zn = ZnCl 2 + Sn2
Neutralization reactions are double reactions that occur between acids and bases. For example, an acid-base reaction produces water and salt. An example is when hydrochloric acid reacts with sodium hydroxide, and the products are sodium chloride, salt, and water.
In this example, HCL is the acid, while NaOH is the base. In a practical example, we can have baking soda reacting with vinegar. The products we mostly use when cleaning our homes.
HCL + NaOH = NaCl + H2O
These are reactions that involve the burning of compounds. For example, reactants like hydrocarbon react with oxygen to produce carbon dioxide and water. These reactions usually produce energy in the form of heat or light.
CH4 + 2 O2 = CO2 +2 H2O
A precipitation reaction is a double replacement reaction and occurs when two soluble salts combine to form an insoluble precipitate.
Iron chloride reacts with sodium hydroxide to form sodium chloride and iron hydroxide.
FeCl3 aq + 3NaOH aq = 3NaCl aq +FeOH3 S/ppt
These are chemical reactions that involve oxidation and reduction. Oxidation is the addition of oxygen, while reduction is the addition of hydrogen (or removal of oxygen)—for instance, the reaction of copper oxide with hydrogen forming copper metal and water. Copper oxide undergoes reduction by losing oxygen atoms, while hydrogen undergoes oxidation by gaining oxygen atoms.
CuO + H2 = Cu + H2O
Again, you can still define an oxidation-reduction reaction as the change of an oxidation number of a molecule, atom, or ion by gaining or losing an electron. Redox reactions are very common and form the basic functions of life, like photosynthesis, respiration, combustion, and rusting. Therefore, to remember the meaning of oxidation, take it as a loss and reduction as a gain.
The elements that exchange electrons in this reaction are known as the oxidizing and reducing agents. An oxidizing agent is an element that accepts electrons and thus oxidizes the other elements. While a reducing agent, it donates electrons reducing other species in a chemical reaction. For more details on the redox reaction, check this article.
As a company, we offer various answers key in this and other topics in Chemistry as follows;
When writing an equation, the left-hand side represents the reactants while the right products. Therefore, an equation should contain stoichiometric coefficients that show the relative amount of the products and reactants.
For an illustration, check this equation.
A aq+B g= Cs +D l, where A and B are reactants, and CD are products
A stoichiometric coefficient is a number that comes before the atoms, molecules, or ions -for instance, 1 Pb(NO3)2 +2KI = 1Pbl2 +2KNO3; in this equation, 1, 2, 1, and 2 are the stoichiometric coefficients for this equation. These numbers are important to help you in balancing chemical equations.
Also, we should indicate the state symbols while writing chemical equation reactions. The state symbols are as follows.
Aqueous – aq
Gas – g
Liquid – l
Precipitate – ppt ( insoluble)
Solid – s
We guide how to identify and write a chemical reaction in words and symbols.
two or more elements combine to form a complex substance
A +B = AB
compounds breakdown to form simpler substances
An element replaces another one in a compound
AB+C = AC +B
When atoms in different compounds trade for positions
Examples: Identify the following chemical reactions.
1. Zinc and lead (II) react to form zinc nitrate and lead–word equation
Zn + Pb(NO3)2 = Zn(NO3)2 + Pb- symbols equation, a single replacement reaction that involves zinc and lead metals. In the reactivity series of metals, zinc appears above the lead, thus why it replaces lead nitrate in this example.
2. 2NaCl aq +F2g = 2 NaFs + Cl2g
The equation represents a single-replacement reaction. Here we have the negatively charged ions, where fluoride replaces chlorine in the compound. Fluoride and chlorine are halogens in the periodic table. Therefore, the halogens at the top usually replace the elements below them.
We give you solutions for identifying the parts of a chemical equation, describing the equation in words and symbols then balancing.
Look at some of the examples below;
1. Sodium plus water form sodium hydroxide and hydrogen. In symbols, sodium (Na), water (H2O), and oxygen (O2)
Na +H2O = NaOH + O2
To balance the equation the answer will be = 2Na + 2H2O = 2Na(OH) + H2
On the reactants side, we have two atoms of sodium, four atoms of hydrogen, and 2 of oxygen. While on the products side, we have two atoms of sodium, two atoms of oxygen, and four atoms of hydrogen, which balances the equation.
2. Aluminum reacts with lead(II) nitrate to give aluminum nitrate and lead metal
2 Al + 3 PB(NO3)2 = 2Al(NO3)3 +3Pb
our equation is complete and balanced. On the reactants side, we have two aluminum atoms, three lead atoms, six nitrogen atoms, and 18 oxygen atoms. We have two aluminum atoms, 6 nitrogen atoms, 18 oxygen atoms, and three lead atoms in the products.
Chemical reactions occur everywhere in our environment. Imagine all the activities in the kitchen, industries, and natural environment; they all involve chemical reactions.
The basic chemical reactions are synthesis, decomposition, and single and double replacement reactions. Other reaction types like precipitation and neutralization still fall under double replacement.
The key to understanding chemical reactions is mastering what happens to reactants and products in each type of reaction. When you grasp this concept, it will be easy to classify chemical reactions. Again, ensure you learn all the symbols of elements and how to write balanced chemical reaction equations. If you need help, you can always place an order with us and our chemistry tutors will assist you.
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