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