Chem Lab Final
How many electrons are in the atom of Magnesium (Mg)?
12
You noticed the aluminium present in the samples you brought back from the exoplanet. How many neutrons does the nucleus of an aluminium atom have? You can click on the periodic table to go there.
14
I also identified potassium in the samples you brought back. How many protons does it have?
19 protons
Alright! Let's try one more time.What is burette reading from the following image
19.15 mL
What is the Atomic Number of Lithium?
3 as the number of proton
How many types of quantum numbers are there?
4
What is the Atomic Number of an atom that has 5 neutrons and 4 electrons?
4-the atom should have as many protons as electrons
What is the first thing you have to do if there is a fire in the lab?
Alert people
What were some limitations of Bohrs atomic mode
All mentioned reasons
How could you prevent this terrible situation from happening?
All options are correct
One of the reasons x-rays and gamma rays can be dangerous is that exposure may lead to the development of tumors. How does exposure to ionizing radiation cause cancer?
Damage to the DNA
Do you know what the three subatomic particles found in an atom are called?
Electrons, Protons, Neutrons
Which region of the electromagnetic spectrum has the highest frequency
Gamma radiation region
In what form should the vehicle's energy be when it is at this point
Half potential energy and half kinetic energy
Good job! What three elements did you find in the star? (Hover over the cards on the wallscreen to see what elements they represent.)
Hydrogen, Sodium, Magnesium
The second element I identified has 26 protons but only 23 electrons. Can you tell me the name of it after consulting the periodic table?
It is a cation of Iron.
The first element I identified has 12 protons. Can you tell me the name of it after consulting the periodic table?
Mg - Magnesium
Are the following atoms the isotopes of the same element?
No, since they don't have the same atomic number
Which of the following hazards does not apply for methanol?
Oxidizing
Which of the elements you tested doesn't have a characteristic metallic appearance?
Phosphorus
We already covered the discovery of electrons and protons, but after Schrodinger developed his atomic model, one last subatomic particle was discovered. Which one?
The Neutron
What would happen to an atom in its ground state, if external energy was applied to the electrons?
The electron would "jump" to an orbital further away from the nucleus
As you can see, there are some black lines in the absorption spectrum. Can you figure out what these are?
The gas cloud acted as a "filter" and absorbed some of the wave-lengths
Look at the image on the wallscreen. What is the connection between the absorption and emission spectrum?
The wavelengths that were absorbed, are the same as the ones emitted (released).
Wait, that's not the ideal place to put the methanol bottle!
Too close to the opening
All this talk about atoms. Let me ask you this: Do you know what the word "Atom" means?
Uncuttable
Here, you can see the absorption spectrum for Hydrogen . What wavelengths does Hydrogen absorb?
Violet, Blue, Cyan, Red
Which of the following represents an isotope for Lithium ( 7 3 Li)
^4 3 Li
What is the Atomic Number of an anion that has 5 neutrons and 4 electrons?
less than 4- an anion should have less protons than electrons
Which are the subatomic particles of an atom (you can lower your labpad to look at them again)?
protons-neutrons-electrons
How are electrons described in the quantum mechanical model?
wave-particles
Applying the trends of oxidation states in the periodic table, what is a likely oxidation state of Chlorine? A simple rule to remember is the oxidation state is for unmixed atoms the same as their charge.
-1
Which group of elements have a full octet of electrons?
Noble gases
What Lab Safety protocols is Lucy violating? You can always explore and have a look at her again.
She is not dressed properly for working in the lab
How many moles of AgNO 3 silver nitrate should we use to be sure that we have excess, no matter which of the three compounds it is?
0.100 mol
Given the connection between Aw and K (Aw=2K) could you use the Ideal Gas Law and derive the Boltzmann constant? Check out again the Ideal Gas Law and keep all parameters constant apart from k[sub]B.
0.69 e— 10^-23 J/Aw
Imagine the two following scenarios: 1. You pour a small amount of non-halogenated solvent into the halogenated waste. 2. You pour a small amount of halogenated solvent into the non-halogenated waste. Which damage analysis is right?
2. is worse than 1.
By performing titration, we will able to determine the titre. The titre is the total volume of solution added to reach the end-point of the titration. Let's practice! If the final burette reading is 28.45 mL and the initial burette reading is 5.60 mL, what is the titre?
22.85 mL
You got that right! Now, what formula should you use to calculate the maximum velocity possible if a roller coaster begins at that height?
3
What is burette reading from the following image?
5.10 mL
Methanol is volatile because it has a low boiling point. Have a look at the safety data sheet. What is the boiling point of methanol?
65 o C
In today's titration, we are reacting NaOH and H 2 SO 4 . For this reaction, what is the pH at the equivalence point?
7
Clchlorine is part of the element family Halogens, which are also known as salt formers. How many valence electrons does Nasodium have when forming an ionic bond with Clchlorine? As you remember, valence electrons are the ones in the outermost shell
8
Marie: I remember you struggled a bit with the hazard symbols. Do you remember the symbol for oxidizing reagents?
A circle with flames
Marie: You are a true safety expert! Do you remember the hazard symbol for oxidizing reagents?
A circle with flames
Why do we not just calibrate the gas thermometer at absolute zero?
Absolute zero cannot practically be produced in any lab setting
Isolated systems maintain the same amount of total energy, even though it may be transformed from one type to another. Which factor below would reduce the total energy of this system over time?
Air resistance
A standard solution is a solution of accurately known concentration. What is a standard solution for titrating sulfuric acid in acid-alkali titration?
Alkali such as sodium hydroxide
To figure out where the fallen out boxes go to in the periodic table wall we need to perform a couple of experiments. Luckily we have all chemical elements in their pure form here in the lab. What kind of experiment would help you categorize some of the elements?
All of the options are correct
Why do you dip the dipper in the reservoir with boiling water once more, after the reading at the boiling nitrogen temperature?
All the mentioned reasons
How would you determine the absolute zero temperature?
Approach it using a gas thermometer at very low pressure
Assuming that the pressure inside the dipper is atmospheric, that means that the inclined line representing the pressure changes is the one presented below. Which is the expected of the pressure if you want to maintain the temperature at 4 o Cfour degrees celsius?
Approximately 750 Torr
Given the Awesome temperatures you assigned to the reference points, could you tell which equation defines the connection between Aw and K? Click the theory button for a reminder about key Kelvin scale reference values
Aw = 2 * K
Why is it important to use demineralized water?
Because demineralized water doesn't contain minerals
How could you physically measure the temperature of an Ideal Gas directly?
By a change in the volume of the Ideal Gas
In order for the gravimetric analysis to be valid we want all of the chloride ions to precipitate. How can we ensure this?
By letting the silver ions be in excess.
There are usually two different types of fire extinguishers: CO2 based extinguishers and foam based extinguishers. Never use a CO2 based extinguisher on a person. Do you know the reason why?
CO2 is freezing cold
Look at the label on the beaker. What does the hazard symbol mean? Explore the label on the beaker before you answer this question
Corrosive
Which of these hazards could be removed by adding small amounts of a certain solution?
Corrosiveness
Based on what you know about their location in the periodic table, what do Cscaesium and Clchlorine react to?
CsCl
Which of the following solvents would be disposed in the halogenated solvent waste?
DCM (Dichloromethane)
When moving from left to right across a period, ionization energy is increasing ? By which other trend is this caused?
Decrease of atomic radius
What should we do to reduce the risk when working with high concentrated acid and base?
Dilute the acid
What is the main function of burette?
Dispense solution in an accurate volume
As the temperature of the gas is increased the molecules in the gas move faster, the pressure on the side walls of the container is also increased. Why?
Due to the increased kinetic energy which results in higher impacts to the walls
Ionizing radiation is a form of electromagnetic radiation that has high enough energy to remove which of theses from an atom?
Electron
What are the different colors caused by that we can see in the flame test?
Electrons falling back into their original shell
So let me ask you once again. What do you have to do if there is an unexpected violent chemical reaction in a bottle?
Evacuate
Explore the hazard symbol on the box. What does it mean?
Explosive
There is some remaining sodium hydroxide-methanol solution that we have to dispose of. This solution poses several hazards, which of the following does NOT apply for the sodium hydroxide-methanol solution?
Explosive
Which symbol depicts an oxidizing reagent?
Far right
What do you think we need to do to help the lake ecosystem?
Find out the acid concentration so we can neutralize it
Lucy: We also just covered electronegativity in class and I heard it's something that one can estimate from the periodic table. Which is the element with the lowest electronegativity
Francium
Great. The total initial energy of the vehicle needs to be higher than this to make it passed the higher than this to make it passed the highest point of this loop. What is the next step to determine how much additional energy the motor should contribute to the starting position?
From this amount, subtract potential energy at the starting position
What is the reaction to describe neutralization reaction of sulfuric acid and sodium hydroxide?
H 2 SO 4 + 2NaOH → Na 2 SO 4 + 2H 2 O
What does the following symbol mean?
Health Hazard
Which position results in the highest amount of potential energy? You can keep playing with the track if you don't know the answer yet.
Highest position
X-rays and gamma rays may be dangerous, but they are also very useful. What are two applications of gamma radiation?
Hospital scans and cancer therapy
What do you think is the reason for an increasing atomic radius within one group?
Increasing number of electron shells
Question 11: What do you think is the reason for a decreasing atomic radius within one period?
Increasing number of protons
Well done! How should you dispose of the remaining methanol solution?
Into organic solvent waste
Good job! Now why is it that the volumetric flask is the right choice here?
It's ideal to mix different substances in, and it has the precision we need
Alright, now you actually have an aqueous solution of your salt! Though perhaps not all of the salt has dissolved yet, but we'll get to that. How sure would you say you are about the concentration at this point?
It's really inaccurate
Which is the unique property of light within the group of electromagnetic waves?
Light waves can be detected by the human eye
Why is it dangerous to wear contact lenses in the lab?
Liquid can be trapped under them
Which mass of vehicle goes the fastest at the bottom? You can continue playing with the track if you don't know the answer yet.
Mass has no effect on velocity
To which of the three main chemical classes does Mercury (Hg) belong to? Don't forget you can read the theory, and look at the periodic table in the Media tab if you are in doubt.
Metals
Why is it important to work in the fume hood during this step?
Methanol gets very volatile at high temperature
Which of the compounds do you think it is? You were very accurate with the experimental procedure, so I would expect the yield to be more than 90 %
MgCl 2
Which of the following parameters affect the zero temperature?
Neither the type of gas nor the initial pressure
You can see one sample of each of the elements we need to correctly assign to the periodic table in front of you. Based on their phase of matter and what you already learned, which of the elements is clearly not a metal?
Neon
Since these 3 vehicles would all go the same speed at the bottom if released from the same height, would they all possess the same amount of kinetic energy?
No, because mass has an effect on kinetic energy
Does the vehicle have zero energy at the bottom of the track?
No, because there is motion.
Lucy: Can you tell me what the green color here in the periodic table stands for
Non-metals
: Have a look at the numbering in the periodic table. In the standard periodic table, the elements are listed in order of increasing atomic number Z. What do you think the atomic number represents?
Number of protons
Have a look at the Hazard Identification section by clicking the 'View Theory' button. Which P-sentence indicates why you should work in the fume hood when using methanol?
P260 and P271
The completion of acid-base titration is represented by end-point and equivalence point. What is end-point?
Point where the indicator changes color
What do we first need to calculate in order to determine the minimum initial velocity of the roller coaster if it is going to complete this double loop?
Potential energy at the top of the loop
Which sentence best describes the relationship between wavelength, frequency, energy and speed? You can view the image from the computer screen by clicking the View Image button.
Shorter wavelengths have higher frequencies
Before I let you go, let's see if can get this last question. What do you do if you add a bit too much solvent when filling the volumetric flask to the mark?
Start over, the solution cannot be saved
Well done, you have proven that you know how to work in a lab. What do you have to do before leaving the lab, to make sure you don't carry traces of chemicals outside?
Take off your lab coat and wash your hands
Excellent work! What was the first step of using the balance, before adding anything to a weighing dish?
Tare the balance with the weighing dish on and the balance closed
Why didn't you just clean the spill with water?
The acid reacts with water
If you want to repeat the same experiment, how can you be sure that you used twice as many molecules as you used in the previous experiment?
The initial pressure in the dipper should be double in size
Look at your lab journal: Can you see from the reaction stoichiometry how the number of moles of AgClsilver chloride formed correlates to the number of moles of AgNO 3 silver nitrate consumed?
The number of moles are the same.
According to the Ideal Gas Law, what happens if you reduce the dipper size to half of the one you're using BUT keep the number of gas molecules inside it the same (PV=nk[sub]B T)?
The pressure would double in size
Which of the following answers is NOT a valid reason for the percentage yield of the reaction being below 100%?
The product is not completely dry
Which value for the absolute zero temperature do you expect to see for different gases?
The same
If the pressure in the gas tank of the dipper was set very high, the Ideal Gas law breaks down. Why is this happening?
The volume occupied by the molecules themselves is no longer negligible
On which of the pictures do you find most particles? By particles I mean, sand grains, water molecules and iron atoms.
There are roughly the same amount of particles on each picture
Look at the reaction schemes in your journal. How does the number of moles of AgNO 3 silver nitrate correlate to the number of moles of the alkaline earth metal chloride?
There should be twice as many moles of AgNO 3 as XCl 2
What do you notice about the components that make up the SI unit for kinetic energy?
They are the same as potential energy.
Lucy: What's up with the other elements that are in the same group as Krypton. Do they have anything in common?
They have the same number of valence electrons
Nice! We have transferred 25 mL of sulfuric acid sample into a volumetric flask. Why do we use a volumetric flask?
To obtain accurate and precise volume
Marie: Why did you decide not to grab the fire extinguisher and fight the fire?
Too dangerous
Marie: I passed out because of the blast. What did you do after you pulled me out of the lab?
Trigger alarm and break the circuit
In the acid-alkali titration, the pH changes quickly from 3 to 10 with equivalence point at pH 7. If we used bromothymol blue as an indicator, when will we reach the end-point?
When the solutions turn from yellow to blue
What should you NOT do if a person's clothes suddenly catch fire?
Wrap a fire blanket around a standing person
Atoms and molecules are way too small to be seen, even with a microscope, so how can we count how many there is?
You count them by mass.
Alright. How do we then get from moles (n) to mass (m)? I'll give you a hint: You're going to need the molar mass (M)
m = n x M
Let's start by figuring out the amount needed in moles. From there, we can easily find the equivalent mass. Which equation do we need to find out how many moles of NH 4 Clsolution of it?
n = C x V
How would you write the conversion reaction from oil to biodiesel?
oil + alcohol + catalyst → biodiesel + glycerol + catalyst
