Search found 67 matches

by Mukil_Pari_2I
Sat Feb 23, 2019 9:35 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: What is residual entropy?
Replies: 3
Views: 6

Re: What is residual entropy?

Residual entropy is the difference in entropy between a non-equilibrium state and crystal state of a substance close to absolute zero.
by Mukil_Pari_2I
Sat Feb 23, 2019 9:35 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: What is the difference between entropy and free energy?
Replies: 2
Views: 4

Re: What is the difference between entropy and free energy?

I would add that Gibbs free energy is the maximum of reversible work that may be performed by a thermodynamic system at a constant temperature and pressure. Entropy is a thermodynamic function that describes the randomness and disorder of molecules based on the number of different arrangements avail...
by Mukil_Pari_2I
Sat Feb 23, 2019 9:33 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: test 3
Replies: 6
Views: 14

Re: test 3

I believe Gibbs free energy is 4J. Additionally, electrochemistry is 6K to 6M.
by Mukil_Pari_2I
Sat Feb 23, 2019 9:31 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 3
Replies: 5
Views: 16

Re: Test 3

^Dr. Lavelle said that we should study based off the homework fro Gibbs Free energy as well as the electrochemistry material.
by Mukil_Pari_2I
Thu Feb 14, 2019 1:18 am
Forum: General Science Questions
Topic: Midterm Formulas
Replies: 6
Views: 49

Re: Midterm Formulas

Most formulas were provided on the midterm. I feel that even those that were not provided could have been figured out based off the ones given too us.
by Mukil_Pari_2I
Thu Feb 14, 2019 1:17 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Stability
Replies: 2
Views: 23

Re: Stability

If the equilibrium constant is larger than 1, that means product formation is favored. If the formation of something is favored, it usually means its the more stable molecule.
by Mukil_Pari_2I
Thu Feb 14, 2019 1:14 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv and Cp
Replies: 3
Views: 24

Re: Cv and Cp

Usually you will be given some information as to the conditions of the situation. Based of that, you should be able to figure out if it is constant pressure or constant volume.
by Mukil_Pari_2I
Thu Feb 14, 2019 1:09 am
Forum: Calculating Work of Expansion
Topic: Integrals
Replies: 4
Views: 23

Re: Integrals

Calculus is probably not required but its a good idea to understand the conceptual backing behind the formulas. That would include the calculus derivations.
by Mukil_Pari_2I
Sat Feb 09, 2019 2:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: midterm [ENDORSED]
Replies: 4
Views: 58

Re: midterm [ENDORSED]

Anjali_Kumar1F wrote:When is Lyndon going to post his midterm review ws??

He will probably post today or tomorrow before his midterm review session on Monday. I would recommend searching up the word "hotdog" to find his worksheet because Dr. Lavelle recommended that to be the name of his worksheet.
by Mukil_Pari_2I
Sun Feb 03, 2019 11:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Work done by expansion
Replies: 3
Views: 15

Re: Work done by expansion

When a gas expands against external pressure, it has to to transfer some of its energy over to the surroundings so it reduces its overall energy because of its negative work.
by Mukil_Pari_2I
Sun Feb 03, 2019 11:51 pm
Forum: Phase Changes & Related Calculations
Topic: Type of systems
Replies: 12
Views: 60

Re: Type of systems

No. Isolated systems don't allow either energy transfers or matter transfers while closed systems still allow energy transfer. For example, closed systems could still absorb heat.
by Mukil_Pari_2I
Sun Feb 03, 2019 11:45 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 47
Views: 449

Re: Midterm [ENDORSED]

Looking up and doing extra practice problems online also helps reinforce key concepts.
by Mukil_Pari_2I
Sat Feb 02, 2019 8:38 pm
Forum: Phase Changes & Related Calculations
Topic: Heat
Replies: 6
Views: 41

Re: Heat

For the reaction, q would be negative if that helps.
by Mukil_Pari_2I
Sat Feb 02, 2019 8:36 pm
Forum: Phase Changes & Related Calculations
Topic: Negative work
Replies: 11
Views: 61

Re: Negative work

Yes, if the force being applied is in the opposite direction of the displacement, the work will be negative.
by Mukil_Pari_2I
Sat Feb 02, 2019 8:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Review
Replies: 14
Views: 98

Re: Midterm Review

Dr. Lavelle said in his email today that he will be announcing when the sessions will be most likely on Tuesday or Wednesday.
by Mukil_Pari_2I
Tue Jan 22, 2019 3:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Setting up Equilibrium Equations
Replies: 2
Views: 20

Re: Setting up Equilibrium Equations

I believe we do need to know how to set up the equation by ourself, however I believe the Ka or Kb value will be given to us or enough information will be given so we can find either value. To set up the equation, you first need to determine whether the molecule dissolved in water is a weak acid or ...
by Mukil_Pari_2I
Tue Jan 22, 2019 3:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: AlCl3 (aq)
Replies: 1
Views: 22

Re: AlCl3 (aq)

Since the Al is a cation, it is surrounded by water molecules. So the equation would be Al(H₂O)₆3+ + H₂O --> H₃O+ + Al (H₂O)₅OH2+
by Mukil_Pari_2I
Tue Jan 22, 2019 3:20 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework for Week 3
Replies: 5
Views: 24

Re: Homework for Week 3

I believe the Chem_Mod said that this week's homework should be from the Acids and Base Chapter and the material we just learned last week.
by Mukil_Pari_2I
Tue Jan 22, 2019 12:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: help with homework 12.57
Replies: 2
Views: 43

Re: help with homework 12.57

For part a, you're given that the pH of 0.10 M HCLO2 is 1.2. pH is -log[H3O+], so to solve for [H3O+] you have to do 10^-pH. In this case, it would be 10^-1.2=0.06 M H3O+. Then, you solve for the Ka (acidity constant), which is (0.06^2)/(0.1-0.06). The pKa is the -log of your Ka value. Part b is th...
by Mukil_Pari_2I
Sun Jan 20, 2019 4:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sig figs in pH
Replies: 7
Views: 36

Re: Sig figs in pH

For pH, the sig figs in the final answer are calculated based off the least amount of sig figs in the answer. Then that amount of sig figs is used after the decimal point.
by Mukil_Pari_2I
Sun Jan 20, 2019 3:11 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Removing products
Replies: 10
Views: 44

Re: Removing products

Only Q should be affected because q is in terms of what is happening during the reaction. K is just the overall equilibrium constant and it should not change.
by Mukil_Pari_2I
Sun Jan 20, 2019 3:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 4
Views: 23

Re: 5% rule

As Dr. Lavelle said in lecture, less than 5% is the rule. You can check with the quadratic formula to confirm though.
by Mukil_Pari_2I
Sun Jan 20, 2019 3:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When x is small
Replies: 4
Views: 15

Re: When x is small

If the approximation is not within 5%, then the answer would not be valid. You would have to use the quadratic equation to figure out the value of x.
by Mukil_Pari_2I
Sun Jan 13, 2019 7:25 pm
Forum: Student Social/Study Group
Topic: New to Lavells's
Replies: 1
Views: 24

Re: New to Lavells's

Dr. Lavelle's tests in 14A were a good balance of computational and conceptual questions. 14A also did not cover deriving things like schrodinger's equation: rather it focused on the concept. Other than that, there really should not be any real difference.
by Mukil_Pari_2I
Sun Jan 13, 2019 7:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient Meaning
Replies: 2
Views: 13

Re: Reaction Quotient Meaning

Well, the reaction quotient Q is supposed to come into play when we try to figure out which direction a reaction is likely to proceed, based of pressure or the concentrations of products and reactants.
by Mukil_Pari_2I
Sun Jan 13, 2019 7:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables
Replies: 3
Views: 20

Re: ICE Tables

I would assume so because in the reaction, the reactants become the products. Therefore it would make sense for there to be a negative x on the reactant side and a positive x on the products side.
by Mukil_Pari_2I
Sat Dec 08, 2018 11:44 pm
Forum: Polyprotic Acids & Bases
Topic: Polyprotics on Final
Replies: 3
Views: 57

Re: Polyprotics on Final

If it has more than h+ proton that can dissasociate.
by Mukil_Pari_2I
Fri Dec 07, 2018 1:01 am
Forum: Bronsted Acids & Bases
Topic: 7th ed 6A.9 c
Replies: 1
Views: 16

Re: 7th ed 6A.9 c

Proton transfers are shown by the transfer of a hydrogen proton. Here, there was no proton transfer. Instead, an OH bond was transferred from acetic acid and replaced with NH2. And the OH bonded with last H atom remaining.
by Mukil_Pari_2I
Fri Dec 07, 2018 12:47 am
Forum: Amphoteric Compounds
Topic: H2O as Amphotertic Compound
Replies: 1
Views: 13

Re: H2O as Amphotertic Compound

No, it is not the only amphoteric compound. Other examples are HCO3 and HSO4.
by Mukil_Pari_2I
Fri Dec 07, 2018 12:43 am
Forum: Administrative Questions and Class Announcements
Topic: Final Exam
Replies: 22
Views: 231

Re: Final Exam

Based off past final exams, the final exam will be a cumulative. Think of it as the midterm but on steroids with the stuff that we just learned.
by Mukil_Pari_2I
Fri Dec 07, 2018 12:35 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka on final, 12.25 [ENDORSED]
Replies: 3
Views: 316

Re: Ka on final, 12.25 [ENDORSED]

BenJohnson1C wrote:Is this also true for the upcoming final? (fall 2018)


Calculating Ka values, based of what Dr. Lavelle has said, will not be on the final.
by Mukil_Pari_2I
Tue Nov 27, 2018 9:41 pm
Forum: Formal Charge and Oxidation Numbers
Topic: TEST 3
Replies: 4
Views: 76

Re: TEST 3

The only equations given are the ones on the sheet given on every test. The Formal charge equation is just FC = Valence - [Lone Pairs + (1/2 Bonding Pairs)]. It would behoove you to memorize it.
by Mukil_Pari_2I
Tue Nov 27, 2018 9:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Exam
Replies: 22
Views: 231

Re: Final Exam

Based off previous finals, its cumulative. Even if Dr. Lavelle does not isolate a concept such as balancing equations, he may give us something where we have to balance the equation as a key step in another related problem. Basically blending concepts.
by Mukil_Pari_2I
Tue Nov 27, 2018 9:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent and Angular
Replies: 5
Views: 50

Re: Bent and Angular

Or you could be safe and write bent/angular on the test.
by Mukil_Pari_2I
Tue Nov 27, 2018 6:18 pm
Forum: Electronegativity
Topic: Electronegativity values
Replies: 2
Views: 31

Re: Electronegativity values

If you want to figure out the which has more ionic character for a specific molecule, just use the general trend to generally find the difference. We will not be expected to calculate the electronegativity difference unless the electronegativity values have been given to us. In the case of the probl...
by Mukil_Pari_2I
Tue Nov 27, 2018 6:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 38
Views: 459

Re: Test 3

Does this mean that the material covered in this past Monday's lecture won't be included? No it as stated on Dr. Lavelle's website, the test will only cover 3.12-3.16, 6.4-6.5, and 4.1-4.7 which do not include Monday's lecture. Hi guys. What do we need to know about Acids and Bases for Test 3? Need...
by Mukil_Pari_2I
Tue Nov 27, 2018 6:01 pm
Forum: Hybridization
Topic: Molecular Shape
Replies: 2
Views: 18

Re: Molecular Shape

When determining hybridizations, you have to take into account molecular shape. When looking at molecular shape, you have to look at both bonded pairs and lone pairs. Furthermore, you have to take into account all of the electron densities on the atom that you are looking at, usually the central ato...
by Mukil_Pari_2I
Fri Nov 23, 2018 8:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 3
Replies: 10
Views: 136

Re: Test 3

A good way to study conceptually is just explaining the concepts to yourself without looking at your notes. For instance, writing the concepts on a whiteboard and explaining it to yourself as you go along writing.
by Mukil_Pari_2I
Thu Nov 22, 2018 4:56 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 3 Question
Replies: 4
Views: 73

Re: Test 3 Question

Dr. Lavelle also posted on his website what the test would cover - Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see Syllabus and Outlines for details).
by Mukil_Pari_2I
Fri Nov 16, 2018 12:38 am
Forum: Administrative Questions and Class Announcements
Topic: Homework Due Week 7
Replies: 10
Views: 151

Re: Homework Due Week 7

Soyoung Park 1H wrote:Is the test over both outlines 3 and 4?


The test will be up to whatever he covers during lecture until a couple days before the test. He will probably specify as we get closer to the test but presumable Outline 3 and 4, since they were not on the last test, will be covered on the next test.
by Mukil_Pari_2I
Fri Nov 16, 2018 12:37 am
Forum: Resonance Structures
Topic: 2.7
Replies: 1
Views: 45

Re: 2.7

Are you talking about the 6th edition 2.7 homework problem? The problem does not talk about resonance structures.
by Mukil_Pari_2I
Mon Nov 12, 2018 9:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th Ed. 2.7: Most important Lewis structure
Replies: 2
Views: 28

Re: 7th Ed. 2.7: Most important Lewis structure

The most important lewis structure would be the most stable, lowest energy lewis structure with the right bond angles.
by Mukil_Pari_2I
Mon Nov 12, 2018 9:44 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electron Distortion
Replies: 2
Views: 41

Re: Electron Distortion

In addition to the aforementioned response, this post from 2016 may help: viewtopic.php?t=16153
by Mukil_Pari_2I
Mon Nov 12, 2018 9:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 3
Replies: 8
Views: 101

Re: Test 3

Every chapter builds on previous concepts we have learned. Whilst it may not be an explicitly cumulative test, there probably still will be concepts in the third test from prior tests (ie dimensional analysis, energy calculations).
by Mukil_Pari_2I
Mon Nov 12, 2018 9:41 pm
Forum: Dipole Moments
Topic: Interaction Potential Energy
Replies: 3
Views: 37

Re: Interaction Potential Energy

At the very least, its a good idea to know the general concept behind the Ep equation even if we are not using it for calculation questions. Also, general rule of thumb, whatever Dr. Lavelle goes over in class is fair game for the third test or the final exam.
by Mukil_Pari_2I
Fri Nov 02, 2018 12:44 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Degenerate orbitals
Replies: 3
Views: 49

Re: Degenerate orbitals

Degenerate orbital are just orbitals that have the same energy level and thus (for hydrogen atoms), the same energy.
by Mukil_Pari_2I
Fri Nov 02, 2018 12:41 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Test Question 1a
Replies: 2
Views: 100

Re: Test Question 1a

For this, you actually have to calc the mass of the nitrogen gas molecule. The way to do that is first find the molar mass of nitrogen (in this case of n2 bc nitrogen is diatomic). Once you have found the molar mass, divide the molar mass by avagadro's number to find how many gs each molecule weighs...
by Mukil_Pari_2I
Sun Oct 28, 2018 10:48 pm
Forum: Lewis Structures
Topic: Delocalized Electrons
Replies: 5
Views: 66

Re: Delocalized Electrons

Its a pretty general term actually. As far as I know, its just not associated with a single atom or a covalent bond.
by Mukil_Pari_2I
Sun Oct 28, 2018 10:44 pm
Forum: Ionic & Covalent Bonds
Topic: Interactions between ions
Replies: 3
Views: 69

Re: Interactions between ions

I don't think so. Just know everything Lavelle goes over in lecture.
by Mukil_Pari_2I
Sun Oct 28, 2018 10:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s state
Replies: 2
Views: 30

Re: 4s state

I am not 100% sure but I believe its because the Aufbau principle indicates that the 4s orbital fills before the 3d orbital and thus the energy is lower in the 4s.
by Mukil_Pari_2I
Wed Oct 24, 2018 9:29 am
Forum: Quantum Numbers and The H-Atom
Topic: Homework questions 2.21 and 2.27
Replies: 4
Views: 612

Re: Homework questions 2.21 and 2.27

it should be 5d. I think "6d" was prolly a typo.
Lina Petrossian 3D wrote:Isn't 2.27 part a) 5d instead of 6d?
by Mukil_Pari_2I
Tue Oct 23, 2018 2:51 pm
Forum: Properties of Light
Topic: calculating wavelength
Replies: 10
Views: 253

Re: calculating wavelength

Dr. Lavelle mentioned that E = hv can only be used for light. However, De Broglie's equation of lambda=h/p can only be used for objects with "rest" mass and velocity. "Rest" mass basically means anything that has mass when stationary. why is rest in quotes.. is there a significa...
by Mukil_Pari_2I
Tue Oct 23, 2018 2:43 pm
Forum: Photoelectric Effect
Topic: Question 28B on Post Module Assessment for Photoelectric Effect
Replies: 1
Views: 71

Re: Question 28B on Post Module Assessment for Photoelectric Effect

So what you need to do is account for the per mol portion of the threshold energy. The energy given was in terms of how much energy is needed to eject 1 mole of electrons of that metal. You need to find how much energy is needed to eject one electron. This can be easily done by dividing by the conve...
by Mukil_Pari_2I
Sun Oct 21, 2018 10:32 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Module Question 27
Replies: 2
Views: 30

Re: Photoelectric Effect Module Question 27

all you need to do is multiply the frequency by plancks constant. The correct answer if you just do hv is 1.99*10^-18 J.
by Mukil_Pari_2I
Sun Oct 21, 2018 5:43 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum numbers
Replies: 5
Views: 60

Re: Quantum numbers

The way to figure it out from my understanding is that 4 is the energy level it is in (the principle quantam number n equals 4 in this case) and f is determined by what l is equal to. In this case, the value of l, which is 3, corresponds with the the l value for the f orbital. Thus the answer, if pu...
by Mukil_Pari_2I
Sat Oct 20, 2018 4:35 pm
Forum: Properties of Light
Topic: De Broglie's equation
Replies: 6
Views: 77

Re: De Broglie's equation

Yes. De broglie's equation (lamba = h / p) is the equation that cannot be used for photons. However, c=lambda/v, E=hv, E = (hc)/lambda, and E=(1/2)mv^2 can all be used with light.
by Mukil_Pari_2I
Thu Oct 18, 2018 8:35 pm
Forum: DeBroglie Equation
Topic: problem 43 6th edition
Replies: 4
Views: 89

Re: problem 43 6th edition

The minimum uncertainty is change in velocity or delta (the triangle) v. In this case, delta v would be 1.65*10^5 m/s.
by Mukil_Pari_2I
Thu Oct 18, 2018 8:21 pm
Forum: Properties of Light
Topic: calculating wavelength
Replies: 10
Views: 253

Re: calculating wavelength

Dr. Lavelle mentioned that E = hv can only be used for light. However, De Broglie's equation of lambda=h/p can only be used for objects with "rest" mass and velocity. "Rest" mass basically means anything that has mass when stationary.
by Mukil_Pari_2I
Thu Oct 18, 2018 8:19 pm
Forum: Photoelectric Effect
Topic: Energy Levels
Replies: 2
Views: 64

Re: Energy Levels

As energy levels increase, the separating space between them becomes smaller and smaller. At "very high" levels, this gives way to a continuous range of all allowed energies. To corroborate this, during office hours, Dr. Lavelle mentioned that the energy levels eventually become a continuu...
by Mukil_Pari_2I
Thu Oct 18, 2018 8:11 pm
Forum: Properties of Light
Topic: Test 2 [ENDORSED]
Replies: 15
Views: 192

Re: Test 2 [ENDORSED]

I thought it was everything until the end of this week no? Like including quantum numbers which we should go over in final lecture of this week.
by Mukil_Pari_2I
Wed Oct 10, 2018 8:40 pm
Forum: Balancing Chemical Reactions
Topic: Seventh Edition- H21 [ENDORSED]
Replies: 3
Views: 130

Re: Seventh Edition- H21 [ENDORSED]

Don't get frustrated about it! It is really just a guess and check most of time and it does take some time. One tip that I have personally incorporated is starting with the least amount of total atoms for the elements in the equation. For instance, if there are 3 atoms of C vs 5 atoms of F I would s...
by Mukil_Pari_2I
Wed Oct 10, 2018 8:33 pm
Forum: SI Units, Unit Conversions
Topic: Scientific Notation
Replies: 7
Views: 111

Re: Scientific Notation

It matters for things like sig figs. For instance, if your answer was 1330. but you only had 3 sig figs to work with, you would put it into scientific notation ie 1.33 *10^3 because this way you have the same answer and you have the right amount of sig figs.
by Mukil_Pari_2I
Wed Oct 10, 2018 8:16 am
Forum: SI Units, Unit Conversions
Topic: Rounding Off of 5
Replies: 7
Views: 173

Re: Rounding Off of 5

This is just a general rule of sig figs that we must use I believe. A lot of the documents on the website do indicate that we should round to the nearest even number. This is because we will be less precise if we just round up (we would overestimate) and if we just round down (we would underestimate...
by Mukil_Pari_2I
Thu Oct 04, 2018 10:07 pm
Forum: Molarity, Solutions, Dilutions
Topic: HW L7
Replies: 3
Views: 59

Re: HW L7

You need to first convert tristearin and o2 (the reactants) to moles. Then using the molar ration of 2 moles of tristearin/163 moles O2, find how much of one reactant is necessary to full react with the other reactant. Then, you can find how much O2 you need to react full with tristearin. Once that ...
by Mukil_Pari_2I
Thu Oct 04, 2018 9:55 pm
Forum: SI Units, Unit Conversions
Topic: Scientific Notation
Replies: 11
Views: 143

Re: Scientific Notation

Use scientific notation when dealing with very big numbers. Otherwise, it will be a lot more difficult to do multiplication and division without it. In addition, always round the number to the least amount of sig figs in the problem. This youtube vid on scientific notation really help me understand ...
by Mukil_Pari_2I
Thu Oct 04, 2018 9:47 pm
Forum: Significant Figures
Topic: Sig Figs
Replies: 3
Views: 46

Re: Sig Figs

Also, for sig fig rounding, if the last digit is above 5 round up (ie 2 sigfigs then 6.56 is 6.7) and if the last digit is below 5 round down (ie 2 sigfigs then 3.44 is 3.4).

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