3.3 The equilibrium constant

<< Chapter < Page

Siyavula textbooks: grade 12 Page 2 / 2

Chapter >> Page >

For the reaction:

$S O_{2} (g) + N O_{2} (g) \to N O (g) + S O_{3} (g)$

the concentration of the reagents is as follows:

[SO $_{3}$ ] = 0.2 mol.dm $^{- 3}$

[NO $_{2}$ ] = 0.1 mol.dm $^{- 3}$

[NO] = 0.4 mol.dm $^{- 3}$

[SO $_{2}$ ] = 0.2 mol.dm $^{- 3}$

Calculate the value of K $_{c}$ .

Write the equation for k $_{c}$
$K_{c} = \frac{[N O] [S O_{3}]}{[S O_{2}] [N O_{2}]}$
Fill in the values you know for this equation and calculate K $_{c}$
$K_{c} = \frac{(0.4 \times 0.2)}{(0.2 \times 0.1)} = 4$

Got questions? Get instant answers now!

For the reaction:

$S (s) + O_{2} (g) ⇌ S O_{2} (g)$

Write an equation for the equilibrium constant.
Calculate the equilibrium concentration of $O_{2}$ if K $_{c}$ =6 and [ $S O_{2}] = 3 m o l . d m^{- 3}$ at equilibrium.

Write the equation for K $_{c}$
$K_{c} = \frac{[S O_{2}]}{[O_{2}]}$

(Sulfur is left out of the equation because it is a solid and its concentration stays constant during the reaction)
Re-arrange the equation so that oxygen is on its own on one side of the equation
$[O_{2}] = \frac{[S O_{2}]}{K_{c}}$
Fill in the values you know and calculate [O $_{2}$ ]
$[O_{2}] = \frac{3 m o l . d m^{- 3}}{6} = 0.5 m o l . d m^{- 3}$

Got questions? Get instant answers now!

Initially 1.4 moles of NH $_{3}$ (g) is introduced into a sealed 2.0 dm $^{- 3}$ reaction vessel. The ammonia decomposes when the temperature is increased to 600K and reaches equilibrium as follows:

$2 N H_{3} (g) ⇌ N_{2} (g) + 3 H_{2} (g)$

When the equilibrium mixture is analysed, the concentration of NH $_{3}$ (g) is 0.3 mol $\cdot$ dm $^{- 3}$

Calculate the concentration of N $_{2}$ (g) and H $_{2}$ (g) in the equilibrium mixture.
Calculate the equilibrium constant for the reaction at 900 K.

Calculate the number of moles of NH $_{3}$ at equilibrium.
$c = \frac{n}{V}$

Therefore,

$n = c \times V = 0.3 \times 2 = 0.6 m o l$
Calculate the number of moles of ammonia that react (are 'used up') in the reaction.
Moles used up = 1.4 - 0.6 = 0.8 moles
Calculate the number of moles of product that are formed.
Remember to use the mole ratio of reactants to products to do this. In this case, the ratio of NH $_{3}$ :N $_{2}$ :H $_{2}$ = 2:1:3. Therefore, if 0.8 moles of ammonia are used up in the reaction, then 0.4 moles of nitrogen are produced and 1.2 moles of hydrogen are produced.
Complete the following table

NH $_{3}$ N $_{2}$ H $_{2}$

Start of reaction 1.4 0 0

Used up 0.8 0 0

Produced 0 0.4 1.2

Equilibrium 0.6 0.4 1.2
Using the values in the table, calculate [N $_{2}$ ] and [H $_{2}$ ]
$[N_{2}] = \frac{n}{V} = \frac{0.4}{2} = 0.2 m o l . d m^{- 3}$

$[H_{2}] = \frac{n}{V} = \frac{1.2}{2} = 0.6 m o l . d m^{- 3}$
Calculate K $_{c}$
$K_{c} = \frac{{[H_{2}]}^{3} [N_{2}]}{{[N H_{3}]}^{2}} = \frac{{(0.6)}^{3} (0.2)}{{(0.3)}^{2}} = 0.48$

Got questions? Get instant answers now!

Hydrogen and iodine gas react according to the following equation:

$H_{2} (g) + I_{2} (g) ⇌ 2 H I (g)$

When 0.496 mol $H_{2}$ and 0.181 mol $I_{2}$ are heated at $450^{o}$ C in a 1 dm $^{3}$ container, the equilibrium mixture is found to contain 0.00749 mol $I_{2}$ . Calculate the equilibrium constant for the reaction at $450^{o}$ C.

Calculate the number of moles of iodine used in the reaction.
Moles of iodine used = 0.181 - 0.00749 = 0.1735 mol
Calculate the number of moles of hydrogen that are used up in the reaction.
The mole ratio of hydrogen:iodine = 1:1, therefore 0.1735 moles of hydrogen must also be used up in the reaction.

Calculate the number of moles of hydrogen iodide that are produced.

The mole ratio of H $_{2}$ :I $_{2}$ :HI = 1:1:2, therefore the number of moles of HI produced is 0.1735 $\times$ 2 = 0.347 mol.

So far, the table can be filled in as follows:

	H $_{2}$ (g)	I $_{2}$	2HI
Start of reaction	0.496	0.181	0
Used up	0.1735	0.1735	0
Produced	0	0	0.347
Equilibrium	0.3225	0.0075	0.347

Calculate the concentration of each of the reactants and products at equilibrium.
$c = \frac{n}{V}$

Therefore the equilibrium concentrations are as follows:

[H $_{2}$ ] = 0.3225 mol.dm $^{- 3}$

[I $_{2}$ ] = 0.0075 mol.dm $^{- 3}$

[HI] = 0.347 mol.dm $^{- 3}$
Calculate K $_{c}$
$K_{c} = \frac{[H I]}{[H_{2}] [I_{2}]} = \frac{0.347}{0.3225 \times 0.0075} = 143.47$

Got questions? Get instant answers now!

The equilibrium constant

Write the equilibrium constant expression, K c for the following reactions:
1. $2 NO (g) + {Cl}_{2} (g) ⇌ 2 NOCl$
2. $H_{2} (g) + I_{2} (g) ⇌ 2 HI (g)$
The following reaction takes place: ${Fe}^{3 +} (aq) + 4 {Cl}^{-} ⇌ {FeCl}_{4}^{-} (aq)$ K $_{c}$ for the reaction is 7.5 $\times$ 10 $^{- 2}$ mol.dm $^{- 3}$ . At equilibrium, the concentration of FeCl $_{4}^{-}$ is 0.95 $\times$ 10 $^{- 4}$ mol.dm $^{- 3}$ and the concentration of free iron (Fe $^{3 +}$ ) is 0.2 mol.dm $^{- 3}$ . Calculate the concentration of chloride ions at equilibrium.
Ethanoic acid (CH $_{3}$ COOH) reacts with ethanol (CH $_{3}$ CH $_{2}$ OH) to produce ethyl ethanoate and water. The reaction is: ${CH}_{3} COOH + {CH}_{3} {CH}_{2} OH \to {CH}_{3} {COOCH}_{2} {CH}_{3} + H_{2} O$ At the beginning of the reaction, there are 0.5 mols of ethanoic acid and 0.5 mols of ethanol. At equilibrium, 0.3 mols of ethanoic acid was left unreacted. The volume of the reaction container is 2 dm $^{3}$ . Calculate the value of K $_{c}$ .

Questions & Answers

what is defense mechanism

Chinaza Reply

what is defense mechanisms

Chinaza

I'm interested in biological psychology and cognitive psychology

Tanya Reply

what does preconceived mean

sammie Reply

physiological Psychology

Nwosu Reply

How can I develope my cognitive domain

Amanyire Reply

why is communication effective

Dakolo Reply

Communication is effective because it allows individuals to share ideas, thoughts, and information with others.

effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.

it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.

miss

Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment

Wekolamo Reply

please i need answer

Wekolamo

because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).

Manix Reply

Agreed 👍 There are many parts of our brains and behaviors, we really need to get to know. Blessings for everyone and happy Sunday!

ARC

A child is a member of community not society elucidate ?

JESSY Reply

Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?

Simon Reply

compare and contrast skinner's perspective on personality development on freud

namakula Reply

Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning

war

explain how nature and nurture affect the development and later the productivity of an individual.

Amesalu Reply

nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.

Samuel

I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills

Zyryn Reply

good👍

Jonathan

and having a good philosophy of the world is like a sandwich and a peanut butter 👍

Jonathan

generally amnesi how long yrs memory loss

Kelu Reply

interpersonal relationships

Abdulfatai Reply

Got questions? Join the online conversation and get instant answers!

Jobilize.com Reply

<< Chapter < Page Page > Chapter >>

Read also:

Get Jobilize Job Search Mobile App in your pocket Now!

100% Free Mobile Applications
Receive real-time job alerts and never miss the right job again

Source: OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2

Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 12 physical science' conversation and receive update notifications?

Ask

	13 AP Key Terms 13 Anatomy of the Nervous System By OpenStax Start Key Terms
	Algebra and trigonometry By OpenStax Read Online Course
	2 Pharmacology Nervous System Essay By Rohini Ajay Start Test
	17 AP Key Terms 17 Endocrine System By OpenStax Start Key Terms
	15 AP Key Terms 15 Autonomic Nervous System By OpenStax Start Key Terms
	6 Microeconomics 06 Elasticity By OpenStax Start Flashcards
	Human A&P 2- Final By Madison Christian Start Flashcards
	Chemistry Practice Test By Sandhills MLT Start Test
	19 AP 19 Cardiovascular System Heart MCQ By OpenStax Start Quiz
	10 AP Key Terms 10 Muscle Tissue Key Terms By OpenStax Start Key Terms

	NH $_{3}$	N $_{2}$	H $_{2}$
Start of reaction	1.4	0	0
Used up	0.8	0	0
Produced	0	0.4	1.2
Equilibrium	0.6	0.4	1.2