What does the pH of a solution have to be in order to be a base?

Answer:

it's a chemical Element

Explanation:

symbol He

atomic number 2.

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:

A solute is a solid which dissolves in a solvent. Muddy water contains water and soil, soil does not dissolve in water

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:

B) 82 protons

Explanation:

The number of protons for an element never change. 82 Is the atomic number for Pb which is how many protons it has. An isotope means it has more neutrons.

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

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:

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:

Partial pressure of H₂ = 0.9556 atm

Explanation:

Given:

Barometric pressure = 753 torr

Vapor pressure of water = 26.74 torr

FInd:

Partial pressure of H₂

Computation:

Partial pressure of H₂ = Barometric pressure - Vapor pressure of water

Partial pressure of H₂ = 733 - 26.74  

Partial pressure of H₂ = 726.26 torr

1 atm = 760 torr

So,

Partial pressure of H₂ = 726.26/760

Partial pressure of H₂ = 0.9556 atm

Answer:

D Trigonal pyramidal

Explanation went over in class:

Answer:

D. Trigonal pyramidal

Explanation:

A P E X !

Answer:

The correct answer is

Explanation:

hope this helps u!!

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:

0.333333 cal/g-°C

Explanation:

Energy = mass x specific heat capacity x temperature change.

(E = mcΔT)

Energy = 100.0 cal

specific heat capacity c= unknown

mass m = 4.0 g

temperature change ΔT = 100 - 25 =75°

100 = 4c(75)

c = 0.333333 cal/g-°C

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:

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

Answer:

The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 of a second.

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:

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:

A. increased competition for resources

Explanation:

Answer:

It has been balanced by using the half-reaction method.

Explanation:

I- and IO3- gives I2

We divide the reaction into two half-reactions

(2 I- >> I2 + 2e-) x5 ( oxidation  : I goes from -1 to 0 )

2 IO3- + 12H+ + 10e- >> I2 + 6H2O ( reduction : I goes from +5 to 0 )

10 I- >> 5I2 + 10e-

2IO3- + 12H+ + 10e- >> I2 + 6H2O

-----------------------------------------------------

10 I- + 2IO3- + 12H+ >> 6I2 + 6H2O

To get the smallest numbers we divide by 2 :

5 I- + IO3- + 6H+ >> 3I2 + 3H2O

It has been balanced by using the half-reaction method. Hence, option B is correct.

A chemical reaction that takes place between an oxidizing substance and a reducing substance.

We divide the reaction into two half-reactions

[tex](2 I^-[/tex] → [tex]I_2 + 2e^-)[/tex] x 5 ( oxidation  : I goes from -1 to 0 )

[tex]2 IO^{3-} + 12H^+ + 10e^-[/tex] → [tex]I_2 + 6H_2O[/tex] ( reduction : I goes from +5 to 0 )

[tex]10 I^-[/tex] →[tex]5I_2 + 10e^-[/tex]

[tex]2IO^{3-} + 12H^+ + 10e^-[/tex] → [tex]I_2 + 6H_2O[/tex]

[tex]10 I^- + 2IO^{3-} + 12H^{+}[/tex]→ [tex]6I_2 + 6H_2O[/tex]

To get the smallest numbers we divide by 2 :

[tex]5 I^- + IO^{3-} + 6H^+[/tex] → [tex]3I_2 + 3H_2O[/tex]

Hence, option B is correct.

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Answer:

neutrons :

Explanation:

Protons are positively charged, while electrons are negatively charged. Neutrons are electrically neutral, as the name suggests. The electric charge, noted Q , is a physical quantity.

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:

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.

Answer:

Atoms consist of a nucleus made of protons and neutrons orbited by electrons.

Isotopes are atoms that have same number of protons but they differ in the number of neutrons and in atomic mass.

Answer:

Isotopes are atoms that have the same numbers of protons but different numbers of neutrons. An ion is an atom that has gained or lost electrons, so it now has more or fewer electrons than it does protons. So an ion has a negative or positive charge.

Hope it helps :)

Answer:

10.2 L of CO₂

Explanation:

Our reaction is:

2C + O₂  →  2CO₂

We convert the mass of C, to moles:

5.50 g / 12g/mol = 0.458 moles

Ratio is 2:2, so if 2 moles of C can produce 2 moles of CO₂ then 0.458 moles of C would produce 0.458 moles of gas.

By the Ideal Gases Law, we know that 1 mol of gas is contained in 22.4L, so:

0.458 mol . 22.4L / 1mol = 10.2 L

Answer:

The solubility of KNO₃ at 40° C is 1 mol/dm³

Explanation:

The solubility of a substance is the number of moles of that substance (solute)  contained in a unit volume of solvent at that particular temperature.

Now, Solubility = n/V where n = number of moles of KNO₃ and V = volume of saturated solution = 50.0 cm³ = 0.05 dm³

n = m/M where m = mass of KNO₃ = 5.05 g and M = molar mass of KNO₃ = 101 g/mol

n = 5.05 g/101 g/mol = 0.05 mol

Solubility = n/V

= 0.05 mol/0.05 dm³

= 1 mol/dm³

So, the solubility of KNO₃ at 40° C is 1 mol/dm³

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:

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:

After the reaction, there will 0.60 g of magnesium oxide and 0.25 g of oxygen gas present in the tube

Explanation:

Equation of the reaction between magnesium and oxygen is given as follows:

2Mg(s) + O₂(g) ---> 2MgO(s)

From the equation of reaction, 2 moles of magnesium reacts with i mole of oxygen gas to produce 1 mole of magnesium oxide

molar mass of magnesium is 24.0 g; molar mass of oxygen gas = 32.0 g; molar mass of magnesium oxide = 40.0 g

Therefore 24 g of magnesium reacts with 32 g of oxygen gas

I.00 g of magnesium will react with (24.0 / 32.0) * 1.00 g of oxygen = 0.75 g of oxygen gas.

Therefore, magnesium is the limiting reagent. Once it is used up, the reaction will stop and the excess oxygen will be left in the tube together with the product, magnesium oxide.

mass of excess oxygen = 1.00 - 0.75 = 0.25 g

mass of magnesium oxide formed = (24.0 / 40.0 g) * 1 = 0.60 g