4.1 Writing and balancing chemical equations

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By the end of this section, you will be able to:
• Derive chemical equations from narrative descriptions of chemical reactions.
• Write and balance chemical equations in molecular, total ionic, and net ionic formats.

The preceding chapter introduced the use of element symbols to represent individual atoms. When atoms gain or lose electrons to yield ions, or combine with other atoms to form molecules, their symbols are modified or combined to generate chemical formulas that appropriately represent these species. Extending this symbolism to represent both the identities and the relative quantities of substances undergoing a chemical (or physical) change involves writing and balancing a chemical equation    . Consider as an example the reaction between one methane molecule (CH 4 ) and two diatomic oxygen molecules (O 2 ) to produce one carbon dioxide molecule (CO 2 ) and two water molecules (H 2 O). The chemical equation representing this process is provided in the upper half of [link] , with space-filling molecular models shown in the lower half of the figure.

This example illustrates the fundamental aspects of any chemical equation:

1. The substances undergoing reaction are called reactants , and their formulas are placed on the left side of the equation.
2. The substances generated by the reaction are called products , and their formulas are placed on the right sight of the equation.
3. Plus signs (+) separate individual reactant and product formulas, and an arrow $\text{(⟶)}$ separates the reactant and product (left and right) sides of the equation.
4. The relative numbers of reactant and product species are represented by coefficients (numbers placed immediately to the left of each formula). A coefficient of 1 is typically omitted.

It is common practice to use the smallest possible whole-number coefficients in a chemical equation, as is done in this example. Realize, however, that these coefficients represent the relative numbers of reactants and products, and, therefore, they may be correctly interpreted as ratios. Methane and oxygen react to yield carbon dioxide and water in a 1:2:1:2 ratio. This ratio is satisfied if the numbers of these molecules are, respectively, 1-2-1-2, or 2-4-2-4, or 3-6-3-6, and so on ( [link] ). Likewise, these coefficients may be interpreted with regard to any amount (number) unit, and so this equation may be correctly read in many ways, including:

• One methane molecule and two oxygen molecules react to yield one carbon dioxide molecule and two water molecules.
• One dozen methane molecules and two dozen oxygen molecules react to yield one dozen carbon dioxide molecules and two dozen water molecules.
• One mole of methane molecules and 2 moles of oxygen molecules react to yield 1 mole of carbon dioxide molecules and 2 moles of water molecules.

so is HCl ionic compound
No, covalent compound ➡️ molecule. As both H and Cl are non-metals and and form covalent bind by sharing valence e-. But can fully ionice in water forming H+ (a proton, a reason for acidity) and Cl- (anion =Chloride) Hydrogen Chloride is a gas at room; Hydrochloric acid = HCl (aq), dissolved in w
Abdelkarim
Form covalenr bond*
Abdelkarim
The question marks are an emoji in the first sentence is an unread emoji. HCl Covalent compund -> molecule
Abdelkarim
what is chemistry
where can I get the test bank or mcqs ? any idea ?
what are the types of intermolecular forces between organic compounds
What is chemistry
scientific study of structure of substances and of the way that they react with other substances
Haider
Thanks
khausar
welcome
Haider
Hi
khausar
hi 2
Haider
whr u from
Haider
are u writing GCE
Equin
Cameroon and u
Equin
hello
Daniel
Please what nuclear fusion and nuclear fission
في التسمية الشائعة للكيتونات يتم للمجموعة التي phenone إضافة لفظ تحتوي على الفينل
what is organic chemistry
what is thyroid land
what is density
A measure of the amount of matter contained by a given volume. The ratio of one quantity to that of another quantity.
Anoruo
mass divided by volume i.e. g/cm^3
Walter
A
lynda
density is the mass per unit volume of a substance
Daniel
A
Fifa
what's molarity?
the concentration of a substance in solution, expressed as the number moles of solute per litre of solution
Anoruo
Please help me solve this question. A is a solution of 0.995mol/dm cube hydrochloride acid. B was prepared by diluting 10cm cube of a saturated solution of sodium trioxocarbonate (iv) to 100cm cube at room temperature. Assuming that 21.50cm cube of A reacted with 25cm cube of B. Calculate: i. Concentration of solution B in mol/dm cube. ii.Solubility of sodium trioxocarbonate (iv) at room temperature. Equation of the reaction: Na2Co3 +2HCL------> 2NaCL +H2O +CO2.
I don't know whether it's ok or not, but the answers I got are: I. 0.428 mol/dm^3 II. 4.54g per 100 g of water
Nazifa
In the first one, I first found out the amount of HCl in mol using moles=concentration x volume. Then I checked the ratio of Na2CO3 to HCl, which is 0.5 to 1. Therefore the moles of Na2CO3 will be half of HCl. Using the amount in moles and the volume as 25 cm^3, I reached my answer!
Nazifa
In the second one, it says that 10 cm^3 has saturated Na2CO3 solution. Using the concentration we found in previous answer, I found out the moles present in 10cm^3. After that, using mass= moles x RFM, I got it's mass. As for the mass of water, we know 1 cm^3 gives 1g, so 10 cm^3 gives 10g.....
Nazifa
Using solubility= mass of solute/mass of solvent x 100, we reach the answer.
Nazifa
Note: we will not use the volume of solution to be 100 cm^3, because then the solution will be dilute.
Nazifa
plz do correct me if I'm wrong!! ☺️
Nazifa
is like the answer is 900
lynda
how can I make citric acid crystals from lemon juice
Write the resonance hybrids of furan and thiophene
Hydrolysis of CH3CH2NO2 with 85% H2SO4 gives? 2/Acetaldehyde is oxidised with potassium dichromate and sulphuric acid gives 3/ When benzyl alcohol is oxidised with KMnO4, the product obtained ? 4/ Benzyl chloride is oxidised with KOH4, the 5/
Hydrolysis of CH3CH2NO2 with 85% H2SO4 gives?
Define reduction in term of loss or gain of oxygen or hydrogen give an example.
Aneela
CuO + Mg → Cu + MgO removing oxygen is reduction. here Mg is reducing agent(loss of electrons)
Haider
reduction >> reduc(+)ion mean (+)ion reduced mean electron gained by (+)ion (+)ion means H(+).
Haider
How what works