Why does this experiment need a water pump?

Answer:

the melting point T = 125.36°C

Explanation:

Given that:

The resistance of a platinum thermometer at  0°C is  [tex]R_o[/tex] = 160.0 ohms

The resistance of a platinum thermometer when immersed in a crucible containing a melting substance [tex]R_t[/tex] = 243.8 ohms

The temperature coefficient at room temperature  20°C = ∝ = 0.00392

The objective is to determine the melting point of this substance

To do that ; at 20°C, the resistance of the platinum thermometer can be calculated as follows:

[tex]R_{20} = R_o(1 + \alpha \Delta T)[/tex]

[tex]R_{20} = 160(1 + (0.00392 \times (20-0)^0C))[/tex]

[tex]R_{20} = 160(1 + (0.00392 \times (20))[/tex]

[tex]R_{20} = 160(1 + (0.0784)[/tex]

[tex]R_{20} = 160(1.0784)[/tex]

[tex]R_{20} = 172.544 \ ohms[/tex]

The resistance of the platinum thermometer at t°C , [tex]R_t[/tex] = [tex]R_{20}(1 + \alpha \Delta T)[/tex]

[tex]243.8 = 172.544(1 + 0.00392 \times (T-20)^0C}[/tex]

[tex]\dfrac{243.8}{ 172.544 }= (1 + 0.00392 \times (T-20)^0C}[/tex]

[tex]1.413 = (1 + 0.00392 \times (T-20)^0C}[/tex]

[tex]1.413-1 = 0.00392 \times (T-20)^0C}[/tex]

[tex]0.413 = 0.00392 \times (T-20)^0C}[/tex]

[tex]\dfrac{0.413 }{0.00392} = (T-20)^0C}[/tex]

105.36°C = (T - 20) °C

T = 105.36°C + 20 °C

T = 125.36°C

Answer:

La clorofila capta la energía luminosa del sol. (verdadero) La fotosíntesis degrada las sustancias orgánicas que nesecitas las células(falso)

Explanation:

La clorofila es la encargada de dar el pigmento de color verde en las plantas y la que transforma la energia luminica en energia quimica, es por eso que es verdadera.

La fotosintesis NO degrada las sustancias organicas, sino que transforma un sustrato inorganico en una fuente energetica organica para las plantas.

Esto se debe por que las plantas o vegetales son autonomas, es decir que se autoabastecen energeticamente sin necesidad de ingerir alimentos como en el caso de los mamiferos.

Answer:

The enthalpy of reaction is -185 kJ

Explanation:

To get the reaction:

 H₂(g) + Cl₂(g) → 2 HCl(g)

you must follow the following steps:

1)  Reactive molecules must break their bonds to obtain their atoms.

H₂(g) → 2 H(g)

Cl₂(g) → 2 Cl(g)

Bond energy (or enthalpy) is the energy required to break one mole of bonds of a gaseous substance. In the case of diatomic molecules with a single bond, it corresponds to the energy necessary to dissociate 1 mole of said substance in the atoms that form it.

Whenever you want to break links you must supply energy, so the link enthalpy will have positive values; while when a mole of bonds is formed energy is released and the bond enthalpy of this process will be negative.

In this case you will then have:

H₂(g) → 2 H(g)           ΔH=436 kJ/mol

Cl₂(g) → 2 Cl(g)         ΔH=243 kJ/mol

So the total energy needed to break all the bonds is:

ΔH=1 mol*436 kJ/mol +1 mol* 243 kJ/mol= 679 kJ

2) The atoms that were obtained in the break of the bonds must be combined to obtain the product.

2 H (g) + 2 Cl (g) → 2 HCl (g)

Being the single bond energy for one mole of 431 kJ H-Cl bonds and considering that two moles of H-Cl bonds are formed, the ΔH is:

ΔH = -2 moles* (432 kJ/mol) = -864 kJ

As mentioned, when a mole of bonds is formed energy is released, the bond enthalpy of this process will be negative.  So the formation of HCl is negative.

Hess's law states that the energy change in an overall chemical reaction is equal to the sum of the energy changes in the individual reactions comprising it. So:

ΔHtotal= -864 kJ + 679 kJ

ΔHtotal= -185 kJ

The enthalpy of reaction is -185 kJ

Answer:

it's a chemical Element

Explanation:

symbol He

atomic number 2.

Answer:

Transition metals (Group C) have different numbers of valence electrons compared to the other groups mentioned. Therefore option C is correct.

Transition metals (Group 3-12) have varying numbers of valence electrons. This is because their valence electrons are located in more than one energy level or subshell.

The number of valence electrons for transition metals can range from 1 to 12, depending on the specific element within the group. The varying numbers of valence electrons in transition metals contribute to their diverse chemical properties and ability to form multiple oxidation states.

Therefore, transition metals (Group C) have different numbers of valence electrons compared to the other groups mentioned.

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Answer:

a.the air has less thermal energy so that the temperature increases

Answer:

4

Explanation:

none of them

they are compounds and mixtures

Answer:

4. none of them

Explanation:

Water is a compound.

Air is a mixture.

Soil is a mixture.

None of them are elements.

Answer:

[tex]\large \boxed{\text{-41.2 kJ/mol}}[/tex]

Explanation:

Balanced equation:    CO(g) + H₂O(g) ⟶ CO₂(g) + H₂(g)

We can calculate the enthalpy change of a reaction by using the enthalpies of formation of reactants and products

[tex]\Delta_{\text{rxn}}H^{\circ} = \sum \left( \Delta_{\text{f}} H^{\circ} \text{products}\right) - \sum \left (\Delta_{\text{f}}H^{\circ} \text{reactants} \right)[/tex]

(a) Enthalpies of formation of reactants and products

[tex]\begin{array}{cc}\textbf{Substance} & \textbf{$\Delta_{\text{f}}$H/(kJ/mol}) \\\text{CO(g)} & -110.5 \\\text{H$_{2}$O} & -241.8\\\text{CO$_{2}$(g)} & -393.5 \\\text{H$_{2}$(g)} & 0 \\\end{array}[/tex]

(b) Total enthalpies of reactants and products

[tex]\begin{array}{ccr}\textbf{Substance} & \textbf{Contribution)/(kJ/mol})&\textbf{Sum} \\\text{CO(g)} & -110.5& -110.5 \\\text{H$_{2}$O(g)} &-241.8& -241.8\\\textbf{Total}&\textbf{for reactants} &\mathbf{ -352.3}\\&&\\\text{CO}_{2}(g) & -393.5&-393.5 \\\text{H}_{2} & 0 & 0\\\textbf{Total}&\textbf{for products} & \mathbf{-393.5}\end{array}[/tex]

(c) Enthalpy of reaction [tex]\Delta_{\text{rxn}}H^{\circ} = \sum \left( \Delta_{\text{f}} H^{\circ} \text{products}\right) - \sum \left (\Delta_{\text{f}}H^{\circ} \text{reactants} \right)= \text{-393.5 kJ/mol - (-352.3 kJ/mol}\\= \text{-393.5 kJ/mol + 352.3 kJ/mol} = \textbf{-41.2 kJ/mol}\\ \text{The total enthalpy change is $\large \boxed{\textbf{-41.2 kJ/mol}}$}[/tex]

Answer:

The filament of a bulb has a high melting point because of the heat generated inside the bulb.

Explanation:

When electricity is concentrating and run through a bulb, it starts to generate heat. Leave it on long enough and it will start to build up a lot of heat. Have you ever tried touching a light bulb when it has been all day? It's scorching to the skin.

Since electricity generates heat, the bulb's filament has to have a high melting point so it doesn't melt, destroy the bulb, and leave you light-less. If the filament has a high melting point, then it is able to withstand heat generated by electricity and provide you light.

Answer:

Spraying perfume in one corner of the room and the smell travels to the other side of the room

Explanation:

Answer:

B

Explanation:

The main aim of lab rules is to minimize the no of accidents

Answer:

A. increased competition for resources

Explanation:

Answer:

Explanation:

20% of C2H6O2 

since its a solution, this means that it has 20g of ethylene glycol and the rest is water.

Molar mass of C2H6O2 = (12 x 2) + (1 x 6) + (2 x 16)

                                        = 62

mole = mass/molar mass

Moles of C2H6O2 = 20/62

                               = 0.322 mol

Moles of water = 80/18

                         = 4.444 mol

mole fraction = mol of solute / tatal mol of solution

Mole fraction of ethylene glycol = 0.322/(0.322 + 4.444)

                                                      = 0.068

Mole fraction of water = 1 - 0.068

                                     = 0.932

Explanation:

According to the periodic table, it has 6 valance electrons in its outermost shell of an atom. so, the valancy must be 2.

we usually subtract the valancy from 8 to no. of electrons if no. of electrons in its outermost shell is more than 5.

so, 8-6=2

is the valancy of sulpher here.

Answer:

See the answer below

Explanation:

Since no fresh air is coming into the elevator while the people are still trapped in it, the breathing of the people will alter the composition of the air inside the lift.

Breathing involves taking-in of oxygen and the release of carbon dioxide. Hence, less and less oxygen will become available within the lift while the concentration of the carbon dioxide keeps increasing as time goes on.

If the people remain trapped for a long time, the oxygen composition of the air inside the elevator will become exhausted, the carbon dioxide concentration will increase, and the people will suffocate due to lack of oxygen.

Answer:

Chemical Changes are also called Chemical Reactions. Chemical reactions involve combining different substances. The chemical reaction produces a new substance with new and different physical and chemical properties. Matter is never destroyed or created in chemical reactions.

Explanation:

Answer:

D. The coefficients of a balanced reaction

Explanation:

Just took an a pex quiz

(I picked C and got it incorrect)

The coefficients of a balanced reaction. Hence, option D is correct.

A balanced equation is a chemical reaction in which the number of atoms for each element in the reaction and oxidation numbers are the same for both the reactants and the products.

To adjust the substance condition, you need to ensure the number of molecules of every component on the reactant side is equivalent to the number of particles of every component on the item side.

To make the two sides equal, we need to duplicate the number of particles in every component until the two sides are equivalent.

Hence, option D is correct.

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Answer:

K = 0.167

Explanation:

The equilibrium constant, K of a reaction, is defined as the ratio of the concentrations of products and concentrations of reactants.

For the reactions:

A + B ⇄ C + D

For the definition, K is:

K = [C] [D] / [A] [B]

K = [4.0M] [4.0M] / [9.6M] [10.0M]

The question is incomplete, the complete question is;

Atom Number of protons Number of electrons Number of neutrons

1 39 39 52

2 40 40 50

3 39 39 54

4 40 40 51

Based on the information that is given, which atom in the table has the highest mass?

a. 1

b. 2

c. 3

d. 4

Answer:

c

Explanation:

The relative atomic mass is given as; number of protons + number of neutrons. If we take the relative atomic mass of each of the options;

1) 39 +52 = 91

2) 40+50 = 90

3) 39 + 54 = 93

4) 40 + 51 = 91

Thus 3 has the highest mass as seen above, hence the answer given.

Answer:

Its valancy is 1.

As it has the formula OH-.

It has valancy 1.

hope it helps..

Answer:

78.01 g/mol

Explanation:

To find the molar mass of Al(OH)₃, we have to look at the mass of each individual element on the periodic table.

Al - 26.98

O - 3(16.00) = 48.00

H - 3(1.01) = 3.03

Now add it all together.

26.98 + 48.00 + 3.03 = 78.01 or 78 g/mol

Hope that helps.

Answer:

Explanation:

GIven that:

The activation energy = 250 kJ

k₁ = 0.380 /M

k₂ = ???

Initial temperature [tex]T_1 =[/tex] 1001 K

Final temperature [tex]T_2 =[/tex] 298 K

Applying the equation of Arrhenius theory.

[tex]In \dfrac{k_2}{k_1 }= \dfrac{Ea}{R}( \dfrac{1}{T_1 }- \dfrac{1}{T_2})[/tex]

where ;

R gas constant = 8.314  J/K/mol

[tex]In \dfrac{k_2}{0.380 }= \dfrac{250 * 10^3}{8,314}( \dfrac{1}{1001 }- \dfrac{1}{298})[/tex]

[tex]In \dfrac{k_2}{0.380 }= -70.8655[/tex]

[tex]\dfrac{k_2}{0.380 }= e^{-70.8655}[/tex]

[tex]\dfrac{k_2}{0.380 }= 1.67303256 \times 10^{-31}[/tex]

[tex]{k_2}= 1.67303256 \times 10^{-31} \times {0.380 }[/tex]

[tex]{k_2}= 6.3575 \times 10^{-32}[/tex]  /M .sec

Half life:

At 1001 K.

[tex]t_{1/2} = \dfrac{In_2}{k_1}[/tex]

[tex]t_{1/2} = \dfrac{0.693}{0.38}[/tex]

[tex]t_{1/2} =[/tex] 1.82368 secc

At 298 K:

[tex]t_{1/2} = \dfrac{0.693}{6.3575 \times 10^{-32}}[/tex]

[tex]t_{1/2} =1.09 \times 10^{31} \ sec[/tex]

Answer: 22.5 percent of incoming solar radiation goes directly to the surface of the Earth and is absorbed.

Explanation: Transfer of radiation through a planet's atmosphere. A planet and its atmosphere, in our solar system, can radiate back to space only as much energy as it absorbs from incoming solar radiation.

Answer:

Explanation:

I have the notes

"Only about 40 percent actually reaches the surface of the earth"

"our atmosphere and clouds reflect bout 40 percent of incoming solar radiation back into outer space"

"The remaining 60 percent is responsible for warming the earth"

"About 20 percent of this radiation is absorbed directly by the atmosphere"

Answer:

36.1%

Explanation:

The following data were obtained from the question:

Mass of hydrated copper sulfate = 2 g

Mass of anhydrous copper sulfate = 1.278 g

Percentage of water =..?

Next, we shall determine the mass of water in the hydrated copper sulfate.

This can be obtained as follow:

Mass of hydrated copper sulfate = 2 g

Mass of anhydrous copper sulfate = 1.278 g

Mass of water =...?

Mass of water = Mass of hydrated copper sulfate – Mass of anhydrous copper sulfate

Mass of water = 2 – 1.278

Mass of water = 0.722 g

Finally, we can obtain the percentage of water in the hydrated copper sulfate as follow:

Mass of water = 0.722 g

Mass of hydrated copper sulfate = 2 g

Percentage of water =..?

Percentage of water = mass of water /mass of hydrate x 100

Percentage of water = 0.722/2 x 100

Percentage of water = 36.1%

Therefore, the percentage of water in the hydrated copper sulfate is 36.1%

Answer:

Tyndall Effect is the phenomenon of scattering of light by particles in a colloid or in a very fine suspension.

Starch solution would show Tyndall effect.

N/B: Heterogeneous mixtures show Tyndall effect.

Answer:The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension. Also known as Willis–Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely proportional to the fourth power of the wavelength, so blue light is scattered much more strongly than red light. An example in everyday life is the blue colour sometimes seen in the smoke emitted by motorcycles, in particular two-stroke machines where the burnt engine oil provides these particles.

Under the Tyndall effect, the longer wavelengths are more transmitted while the shorter wavelengths are more diffusely reflected via scattering. The Tyndall effect is seen when light-scattering particulate matter is dispersed in an otherwise light-transmitting medium, when the diameter of an individual particle is the range of roughly between 40 and 900 nm, i.e. somewhat below or near the wavelengths of visible light (400–750 nm).

It is particularly applicable to colloidal mixtures and fine suspensions; for example, the Tyndall effect is used in nephelometers to determine the size and density of particles in aerosols and other colloidal matter (see ultramicroscope and turbidimeter).

It is named after the 19th-century physicist John Tyndall.

Explanation:

Answer:

D Trigonal pyramidal

Explanation went over in class:

Answer:

D. Trigonal pyramidal

Explanation:

A P E X !

Answer:

  O-2

Explanation:

We assume your reference point is 12 units to the left of the position designated as 12. Then 14 unit to the left will be 2 units left of O, or O-2.

An object starts at position 12 on a horizontal line with a reference point of 0. What is the position of the object if it moves 14 units to the left?

THE ANSWER IS -2

Answer:

(b)

Explanation:

The 3s^2, 3p^6  orbitals form  -3 charge.

This is the element phosphorous and an example of a -3 ion is in aluminium phosphide, AlP3.

The electronic configuration which represents the element forming a simple ion having with a charge of -3 is; 1s², 2s², 2p⁶, 3s², 3p³. Option B is correct.

In this electronic configuration, the element has a total of 16 electrons. To form a simple ion with a charge of -3, the element needs to gain three electrons. This is achieved by adding three extra electrons to the existing configuration.

When the element gains three electrons, the electron configuration becomes:

1s², 2s², 2p⁶, 3s², 3p⁶

This configuration represents the stable octet configuration, where the element has a complete outer shell with eight electrons. Since the charge is -3, it means the element has gained three extra electrons to achieve a stable configuration.

Therefore, the correct electronic configuration representing the element that forms a simple ion with a charge of -3 is 1s², 2s², 2p⁶, 3s², 3p³

Hence, B. is the correct option.

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Answer:

About 2 liters

Explanation:

Since 1 gallon equals 3.785 liters, you figure out how many liters per week she uses by 3.785 x 0.75 which is 2.83875. Then divide that by 7 which is 0.405535 liters per day. Then multiply that by 5 days which is 2.027 liters in 5 days.