A student was performing a separation of a mixture of organic compounds. The final step of the process involved a filtration of the analyte from an aqueous solution. After drying the filtered solid for a very short period time, they took the melting point of the compound. The measured melting point range of the compound was 106 – 113.8 0C, while the literature melting point of the compound was 122.3 0C. The above scenario is a very common one in organic labs.
1. Do you think their sample was pure?
2. If not, then what do you think could be the source of error.
3. How do you think this error can be minimized?

Answer:

[tex]\rm Sn[/tex], [tex]\rm Se[/tex], [tex]\rm S[/tex], [tex]\rm Si[/tex].

Explanation:

The relative atomic mass of an element is numerically equal to the mass (in grams) of one mole of its atoms. This quantity can help estimate the number of moles of atoms in each of these four [tex]10.0\; \rm g[/tex] samples.  

Look up the relative atomic mass for each of these four elements (on a modern periodic table.)

The relative atomic mass of [tex]\rm Si[/tex] is (approximately) [tex]28.085[/tex]. Therefore, the each mole of silicon atoms would have a mass of approximately [tex]28.085\; \rm g[/tex]. How many moles of silicon atoms would there be in a [tex]10.0\; \rm g[/tex] sample?

Given:

Number of mole of silicon atoms in the sample: [tex]\displaystyle n(\mathrm{Si}) = \frac{m(\mathrm{Si})}{M(\mathrm{Si})} = \frac{10.0\; \rm g}{28.085\; \rm g \cdot mol^{-1}}\approx 0.356\; \rm mol[/tex].

Similarly:

[tex]\displaystyle n(\mathrm{S}) = \frac{m(\mathrm{S})}{M(\mathrm{S})} = \frac{10.0\; \rm g}{32.06\; \rm g \cdot mol^{-1}}\approx 0.312\; \rm mol[/tex].

[tex]\displaystyle n(\mathrm{Se}) = \frac{m(\mathrm{Se})}{M(\mathrm{Se})} = \frac{10.0\; \rm g}{78.971\; \rm g \cdot mol^{-1}}\approx 0.127\; \rm mol[/tex].

[tex]\displaystyle n(\mathrm{Sn}) = \frac{m(\mathrm{Sn})}{M(\mathrm{Sn})} = \frac{10.0\; \rm g}{118.710\; \rm g \cdot mol^{-1}}\approx 0.0842\; \rm mol[/tex].

Therefore, among these [tex]10.0\; \rm g[/tex] samples:

[tex]n(\mathrm{Sn}) < n(\mathrm{Se}) < n(\mathrm{S}) < n(\mathrm{Si})[/tex].

It is not a coincidence that among these four samples, the one with the fewest number of atoms corresponds to the element with the largest relative atomic mass.

Consider two elements, with molar mass [tex]M_1[/tex] and [tex]M_2[/tex] each. Assume that [tex]n_1[/tex] moles and [tex]n_2[/tex] moles of atoms of each element were selected, such that the mass of both samples is [tex]m[/tex]. That is:

[tex]m = n_1\cdot M_1[/tex].

[tex]m = n_2\cdot M_2[/tex].

Equate the right-hand side of these two equations:

[tex]n_1 \cdot M_1 = n_2\cdot M_2[/tex].

[tex]\displaystyle \frac{n_1}{n_2} = \frac{M_2}{M_1} = \frac{1/M_1}{1/M_2}[/tex].

In other words, the number of moles atoms in two equal-mass samples of two elements is inversely proportional to the molar mass of the two elements (and hence inversely proportional to the formula mass of the two elements.) That explains why in this question, the sample containing the smallest number of atoms corresponds to element with the largest relative atomic mass among those four elements.

Answer:Because plastic products are durable, they can last for a long time. This makes them affordable because they do not have to be replaced often. On the other hand, the popular use of plastics means that many plastics are thrown away. Plastics litter the ocean, causing harm to marine birds and mammals. Plastic breaks down into plastic dust, which can last for up to a thousand years.

^^^^^copy and paste this part^^^^^

Explanation:Plastic is he hardest material to break down with harm to sea life and land life they may be affordable but costly to the environment.

Answer:

D. Electrons: Negative.

Explanation:

Hello, happy to help you today!

In this case, by considering the Bohr's atomic model in which atom is composed by a nuclei containing both protons and neutrons which are positively and neutrally charged respectively and surrounding electrons assembled in orbits or levels of energy which are negatively charged in order to provide a balance to the atom, the correct statement is: D. Electrons: Negative. Also consider the Bohr's model on the attached picture.

My best regards to you!

Answer:

Particles become closer together / contract?

Explanation:

as particles cool down in temp, the particles slow down and compress

Answer:

B) The closer an electron is to the nucleus the lower it's energy level.

Explanation:

This is because the attractive force for electrons to the nucleus is stronger. Thus, the orbital energy becomes less.

Answer:

Arsenic.

Explanation:

Hello there!

In this case, since insecticides are substances that act as poisons to get rid of insects in order to prevent their presence and/or reproduction in houses, companies, crops and others, a substance that has been widely used is the metalloid arsenic due to its direct affection of the insect's body (movement, performance, cellular functions).

In addition, high levels of arsenic in food could cause arsenic poisoning in humans as well, that is why such practice must be properly performed and by using the correct security protocol.

Best regards!

Answer:

As

Explanation:

hoffe das hilf jedem in der zukunft

Answer:

Wind, water, gravity, and ice

Explanation:

Water can erode soil material. Especially if the soil is bare, dry and erodible erosion via rain particles can occur. Wind is another factor that cause soil erosion. Dry soil particles( Especially if they are fine) can move to other areas if wind exists. Ice is another issue on erosion. Ice, when it is melting, can carry soil particles.

Answer:

1,869.97 grams of Be(NO3)2

Explanation:

Be(NO3)2 = Be  N2  O6

Be=9.012182g/mole

N2=28.0134g/mole

O6=96g/mole

therefore Be(NO3)2 gives you 187.56g in one mole

so 9.97 moles means there is 9.97 times more

9.97mole Be(NO3)2 * 187.56g Be(NO3)2/1mole Be(NO3)2 = 1,869.97g of Be(NO3)2

Answer:

0.42 g/cm3

Explanation:

Answer:

20/40=0.5 g/cm^3 becuase, mass/volume=density

Explanation:

Answer:

Pb2+(aq) + 2Cl–(aq) ----> PbCl2(s)

Explanation:

The net ionic equation shows the main reaction that takes place in a system. Hence, a net ionic equation focusses only on those species that actually participate in the reaction.

For the reaction between Pb(NO3)2 and NH4Cl , the net ionic equation is;

Pb^+(aq) + 2Cl^-(aq) ---> PbCl2(s)

The correct net ionic equation for the reaction that occurs when solutions of Pb(NO₃)₂ and NH₄Cl are mixed is

To know the the correct net ionic equation for the reaction that occurs when solutions of Pb(NO₃)₂ and NH₄Cl are mixed, we shall write the net ionic equation for the reaction. This is illustrated below:

Pb(NO₃)₂(aq) —> Pb⁺(aq) + NO₃¯(aq)

NH₄Cl(aq) —> NH₄⁺(aq) + Cl¯(aq)

Pb(NO₃)₂(aq) + NH₄Cl(aq) —>

Pb⁺(aq) + NO₃¯(aq) + NH₄⁺(aq) + Cl¯(aq) —> PbCl₂(s) + NO₃¯(aq) + NH₄⁺(aq)

Cancel the spectator ions (i.e NO₃¯ and NH₄⁺) and write 2 before Cl¯ to obtain the net ionic equation as shown below:

Thus, the correct net ionic equation for the reaction that occurs when solutions of Pb(NO₃)₂ and NH₄Cl are mixed is

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The average atomic mass is given by the individual atomic masses of the isotope of the element and its percentage. The average atomic mass of the isotopic mixture is 159.8 g/mole.

Isotopes are atoms of the same element that have the same number of protons in their nucleus but have a different number of neutrons that alters their atomic masses. The relative abundance of the isotope of the element affects the average atomic mass of the mixture.

The formula for average atomic mass for the mixture of isotopes is given as:

Average atomic mass = ∑ (mass × abundance)

Given,

Abundance of isotope 1 = 22.00 %

Mass of isotope 1 = 159.3 g/mole

Abundance of isotope 2 = 78.00 %

Mass of isotope 2 = 161.2g/mole

Substituting values in the formula of average atomic mass as:

Average atomic mass = isotope 1 (mass × abundance) + isotope 2 (mass × abundance)

= (0.22) × (159.3) + (0.78) × (161.2)

= 34.046 + 125.736

= 159.8 g/mole

Therefore, the average atomic mass of the mixture of the two isotopes is 159.8 g/mole.

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Answer:

N=2

H=6

Explanation:

1.Balance a chemical equation in terms of moles.

2.Use the balanced equation to construct conversion factors in terms of moles.

3.Calculate moles of one substance from moles of another substance using a balanced chemical equation.

The law of conservation of matter says that matter cannot be created or destroyed. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products.

(P.s it could also be where you have to solve it in which you have to simplify it first then solve it.) like adding them all up.

Hope this is the answer. :)

Answer:

pressure

Explanation:

pressure is the amount of force exerted on an area. when you blow up the balloon you're filling it with gas particles. the gas particles move freely within the balloon and may collide with one another exerting pressure on the inside of the balloon.

The pressure of the gas is the amount of force that is exerted on a balloon by the gas inside the balloon. Therefore, option B is correct.

Pressure can be described as the force applied perpendicular to the surface of a body per unit area. Pressure can be defined as a standard mechanical quantity and is derived from a unit of force divided by a unit of area.

The SI unit of measurement of pressure, the pascal (Pa) or Newton per square meter (N/m²). Pressure can be defined as the amount of force exerted perpendicular to the surface per unit area.

Mathematically, the pressure exerted by force can be calculated as:

[tex]{\displaystyle p={\frac {F}{A}}}[/tex]

where, p is the pressure, F is the magnitude of the normal force, and A is the area of the surface.

Therefore, the amount of force that is exerted on the balloon by the gas inside the balloon is equal to pressure.

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Answer:

The answer is "order will be A > F > B> D > G > C > E".

Explanation:

Answer:

[H⁺] = 0.00175 M

pH = 2.757

Explanation:

The ionization of benzoic acid is given below:

C₆H₅COOH ----> C₆H₅COO⁻(aq) + H⁺(aq)

1 mole of H⁺ ions are produced from the dissociation of 1 mole C₆H₅COOH.

Therefore 0.050 M benzoic acid produces 0.050 M H⁺.

However, the benzoic acid is only 3.5% ionized, therefore concentration of H+ ion, [H⁺] = 3.5/100 * 0.050 M

[H⁺] = 0.00175 M

pH = - log[H⁺]

pH = - log(0.00175)

pH = 2.757

Answer:

def compute_volume(pressure,moles,temperature):

    volume = (8.314 * moles * temperature)/pressure

    print("Volume: "+str(volume))

Explanation:

This line defines the function

def compute_volume(pressure,moles,temperature):

This line calculates the volume

    volume = (8.314 * moles * temperature)/pressure

This line prints the calculated volume

    print("Volume: "+str(volume))

Answer:

The correct answer is 0.67 g H₂

Explanation:

Isopropyl alcohol (C₃H₇OH) can decompose to give acetone (C₂H₆OH) and hydrogen gas (H₂) according to the following chemical equation:

C₃H₇OH (g) ⇒ C₂H₆CO(g) + H₂(g)

We can calculate the initial mass of isopropyl alcohol from the density and volume data:

density = m/V = 0.785 g/mL

⇒ m = density x V = 0.785 g/mL x 25.6 mL = 20.096 g C₃H₇OH

According to the chemical equation 1 mol of C₃H₇OH gives 1 mol H₂. The molar mass of C₃H₇OH is:

molar mass C₃H₇OH = (12 g/mol x 3) + (1 g/mol x 7) + 16 g/mol + 1 g/mol = 60 g/mol

molar mass H₂ = 1 g/mol x 2 = 2 g/mol

So, we obtain: 2 g H₂ from 60 g C₃H₇OH. We multiply this stoichiometric ratio (2 g H₂/60 g C₃H₇OH) by the initial mass of C₃H₇OH to obtain the mass of H₂ is formed:

20.096 g C₃H₇OH x (2 g H₂/60 g C₃H₇OH) = 0.6698 g ≅ 0.67 g H₂

Answer:

See explanation

Explanation:

Number of moles of naphthalene = 0.32g/128.1705 g/mol = 0.0025 moles

Molality = number of moles/ mass of Solvent in kilograms

Molality = 0.0025/0.025 Kg

Morality = 0.1 m

But

∆T= K × i × m

Where ∆T = boiling point elevation

i= number of particles (this is equal to 1 because naphthalene is molecular and not ionic)

m= molality of naphthalene = 0.1 m

K= boiling point elevation constant = 5.12 °C/m

∆T= 5.12 °C/m ×0.1 = 0.512°C

For freezing point depression

∆T= K× i × m

Where ∆T= freezing point depression

i= number of particles (this is equal to 1 because naphthalene is molecular and not ionic)

m= molality of naphthalene = 0.1 m

K= freezing point depression constant = 2.67 °C/m

∆T= 2.67 °C/m ×0.1 = 0.267°C

From Raoult's law;

∆P = XBPA°

Where;

∆P = vapour pressure lowering

XB = mole fraction of solute

PA° = vapour pressure of pure solvent

Number of moles of solvent = mass/molar mass = 25g/ 78 g/mol= 0.3205 moles

Total number of moles = number of moles of solute + number of moles of solvent = 0.0025 moles + 0.3205 moles = 0.323 moles

Mole fraction of solute = 0.0025 moles/0.323 moles = 0.0077

Vapour pressure of benzene = 100 torr

Therefore;

∆P = 0.0077 × 100torr = 0.77 torr

Hence;

∆P = 0.77 torr

Answer:

The correct option is C

Explanation:

Chemical equilibrium is a state in which there is no net change in the amount of reactant and products formed over time. This reaction is a reversible reaction, hence the reaction can keep proceeding in either direction until the products formed are equal in mass to that of the reactants or the products been reversed back to the reactants until both sides (product and reactant) achieve equal mass.

Answer:

Mass of nitrogen dioxide produced = 4.6 g

Explanation:

Given data:

Volume of ammonia = 2.30 L

Mass of nitrogen dioxide produced = ?

Solution:

Chemical equation:

4NH₃ + 7O₂     →      4NO₂ + 6H₂O

Number of moles of ammonia at STP:

PV = nRT

n = PV/RT

n = 1 atm × 2.30 L / 0.0821 atm.L/K.mol × 273 K

n = 2.30 atm .L / 22.414 atm.L/mol

n = 0.1 mol

Now we will compare the moles of ammonia with nitrogen dioxide from balance chemical equation.

                NH₃            :             NO₂

                 4                :               4

                 0.1             :              0.1

Mass of NO₂:

Mass = number of moles  × molar mass

Mass = 0.1 mol  × 46 g/mol

Mass = 4.6 g

Answer:

69.94% iron by mass.

Explanation:

Answer:

B :)

Explanation:

The cells that perform the specific function in an organism so it should be specialized.

It is the cell that should be made up of tissued also with the system so that it should be working together in our bodies. It includes the examples like blood cells, nerve cells, reproductive cells. Also, they have their own functions.

Therefore, we can conclude that The cells that perform the specific function in an organism so it should be specialized.

Hence, the option b is correct.

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Answer:

The options are

A.Surroundings get colder and the system decreases in volume.

B.Surroundings get hotter and the system expands in volume.

C.Surroundings get hotter and the system decreases in volume.

D.Surroundings get hotter and the system does not change in volume.

From the Most energy released to the most absorbed , the order is

B. Surroundings get hotter and the system expands in volume.

D. Surroundings get hotter and the system does not change in volume.

C. Surroundings get hotter and the system decreases in volume.

A. Surroundings get colder and the system decreases in volume.

Answer:

Generally described, the input/output device includes a housing for one or more input components such as a keyboard and/or microphone, one or more output components such as a display screen or a speaker, a data storage device such as a hard drive, a processor, and a phone interface.

An input mechanism to allow the user to interact with the phone. The most common input mechanism is a keypad, but touch screens are also found in smartphones. Basic mobile phone services to allow users to make calls and send text messages. All GSM phones use a SIM card to allow an account to be swapped among devices.

The maximum possible power output of a handheld cellular phone is 0.6 watts. Like others have posted, the system controls the actual output of the phone and it is typically much less than that, usually less than 100 milliwatts.

Explanation:

Answer:

true

hope this helps :)

Explanation:

True, [tex]BrF_5[/tex] (aq) is a good insulator.

A material or an object that does not easily allow heat, electricity, light, or sound to pass through it.

Bromine pentafluoride appears as a colourless, fuming liquid with a pungent odour. Used to make other chemicals and in rockets.

Hence,  [tex]BrF_5[/tex] (aq) is a good insulator.

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Al2(SO4)3 aluminium sulfate

Answer:

heterogeneous

Explanation:

It's a heterogeneous mixture. Diamond is made of just one element: carbon. Each carbon atom in diamond is connected to four other carbon atoms, in a crystal that extends on and on. There are other forms of pure carbon where the atoms are bonded differently, notably charcoal and graphite.