Which scientist was the first to practice the scientific method we use today
En Hedu'Anna

Aristotle

Archimedes

Answer:

[H3O+] = 0.0440M

[OH-] = 2.27x10⁻¹³M

Explanation:

Based on the equilibrium of water:

2H2O ⇄ H3O+ + OH-

K = 1x10⁻¹⁴ = [H3O+] [OH-] (1)

We can determine [OH-] with [H3O+] or vice versa

As HCl is a strong acid, [HCl] = [H3O+]

That means:

[H3O+] = 0.0440M

And [OH-] is:

1x10⁻¹⁴ / [H3O+] = [OH-]

2.27x10⁻¹³M = [OH-]

Taking into account the definition of pH and pOH, the hydronium ion, H₃O⁺, and hydroxide ion, OH−, are 0.044 M and 2.29×10⁻¹³ M respectively.

First of all, pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.

The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:

pH= - log [H⁺]= - log [H₃O⁺]

Similarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

The following relationship can be established between pH and pOH:

pOH + pH= 14

In this case, you have a 0.044 M HCl.   HCl is a strong acid.

It is called strong acid, that acid that dissociates completely in solution at constant temperature and pressure. Under these conditions, the concentration of a strong acid is equal to the concentration of hydrogen ions (Hydronium or H₃O⁺). Then, in this case:

[H⁺]=  [H₃O⁺]= [HCl]= 0.044 M

Replacing in the definition of pH:

pH= -log (0.044 M)

Solving:

pH= 1.36

Considering the relationship established between pH and pOH:

pOH + 1.36= 14

pOH= 14 -1.36

pOH= 12.64

Finally, replacing in the definition of pOH:

12.64= -log [OH-]

[OH-]= 10⁻¹² ⁶⁴

[OH-]= 2.29×10⁻¹³ M

In summary, the hydronium ion, H₃O⁺, and hydroxide ion, OH−, are 0.044 M and 2.29×10⁻¹³ M respectively.

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Answer:

K⁺ and HPO₄²⁻ ions are present in K₂HPO₄

Explanation:

K₂HPO₄ consist of anion and cation such as HPO₄²⁻ and  K⁺. We can see that the charge on HPO₄²⁻ is negative 2. Thus inroder to balance the charge and to neutral the compound two potassium ions are attached because the charge on one atom of potassium is K⁺.

Properties of K₂HPO₄ :

It is salt of phosphoric acid.

Its density is 2.44 g/cm³.

It is odourless compound.

It is white powder and soluble in water.

It is used in fertilizer because it provide phosphorus which is beneficial for the growth of plants.

It is also used as a additive in food.

It is inorganic compound and also used as buffering agent.

Answer:

BaI2

Explanation:

Barium gives a green flame test. When the halide test is conducted, a yellow precipitate indicates the presence of the iodide ion.

Also, BaI2 reacts with ammonium carbonate as shown below:

BaI2(aq) + (NH4)2CO3(aq) → BaCO3(s) + 2(NH4)I(aq)

The BaCO3(s) separates from the reaction system as a precipitate.

Answer:

The answer would be D they are the first group on the periodic table.

Explanation:

Answer:

b. organs

Explanation:

molecules combine to form cells, cells combine to form tissues, tissues combine to form organs, organs combine to form organ systems, and organ systems combine to form organisms.

Answer:

B. Organs

Explanation:

Cell - Tissue - Organs - Organ Systems - Organism

Answer:

Explanation:

2 H₂S(g)   +   3O₂(g)  =  2 H₂O(g)   +   2SO₂(g)

2 moles           3 moles                         2 moles

1380 g of H₂S = 1380 / 34 = 40.588 moles of H₂S

6890 g of oxygen  = 6890 / 32 = 215.31 moles of oxygen

Here H₂S is limiting reagent .

2 mole of H₂S  reacts to give 2 moles of sulfur dioxide .

40.588 moles of H₂S will react to give 40.588 moles of sulfur dioxide.

sulfur dioxide formed = 40.588 moles

= 40.588 x 64 = 2597.63 g of sulfur dioxide.

The maximum amount of sulfur dioxide is 2597.63 g of sulfur dioxide.

Since

2 H₂S(g)   +   3O₂(g)  =  2 H₂O(g)   +   2SO₂(g)

So,

2 moles           3 moles                         2 moles

Now

= 1380 g of H₂S

= 1380 / 34

= 40.588 moles of H₂S

Now

= 6890 g of oxygen

= 6890 / 32

= 215.31 moles of oxygen

Here H₂S represents limiting reagent .

2 moles of H₂S  reacts to provide 2 moles of sulfur dioxide .

Now

40.588 moles of H₂S will react to provide 40.588 moles of sulfur dioxide.

Also,

sulfur dioxide formed = 40.588 moles

So,

= 40.588 x 64

= 2597.63 g of sulfur dioxide.

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Answer:

Alchemy

Explanation:

Alchemy is the believe that base metals such as a copper, lead etc can be transmuted into gold.

The alchemists were in search of a magical piece that would enable them to make gold from base metals. They called this magical stuff 'the Philosopher's Stone'.

Modern science has discovered that lead can be turned into gold,without applying the methods of alchemy. Nuclear transmutation in particle accelerators can indeed change one element into another.

Answer:

[tex]V_2=76.0mL[/tex]

Explanation:

Hello.

In this case, given the initial masses of both octane (C8H18, molar mass = 114 g/mol)) and oxygen (O2, molar mass = 32 g/mol), we can compute their moles and subsequently the total pressure via the ideal gas equation at 33 °C into the 250-mL:

[tex]n_{octane}=0.42g*\frac{1mol}{114g} =3.7x10^{-3}mol\\\\n_{oxygen}=0.24g*\frac{1mol}{32g} =7.5x10^{-3}mol\\\\n_T=7.5x10^{-3}mol+3.7x10^{-3}mol=0.0112mol\\\\P_1=\frac{n_TRT}{V_1}=\frac{0.0112mol*0.082\frac{atm*L}{mol*K}*(33+273.15)K}{0.25L}=1.1atm[/tex]

After that, via the Boyle's law, we compute the final pressure in the cylinder and piston system:

[tex]P_1V_1=P_2V_2\\\\V_2=\frac{P_1V_1}{P_2} =\frac{250mL*1.1atm}{3.7atm}\\ \\V_2=76.0mL[/tex]

Best regards!

Answer:

diiodomethane

Explanation:

The densities of each of the liquids mentioned in the question are stated below;

CCl4- 1.59 g/cm^3

Hexane- 0.672 g/cm^3

Benzene- 0.8765 g/cm^3

Diiodomethane- 3.3 g/cm^3

Clearly, the density of diiodomethane methane is almost the same as that of the desired granular material, hence the undesired granular material having a density of 2.04 g/cm3 will float in diiodomethane thus separating the two granular materials.

Answer:D Diffusion

Explanation:

Because the the cell Is letting it go diffuse it to remove it.

Answer:

0.266 moles of Na⁺

Explanation:

First step we dissociate the salt:

Na₃AsO₄  →  3Na⁺  +  AsO₄⁻³

From 1 mol of sodium arsenate, we must have 3 moles of sodium cation and 1 mol of arsenate.

We determine the moles of salt:

18.4 g . 1 mol/ 207.89 g = 0.0885 moles of salt.

We apply the followring rule of three:

1 mol of salt has 3 moles of Na⁺

0.0885 moles of salt may have (0.0885 . 3) / 1 = 0.266 moles of Na⁺

Answer:

1. or A

Explanation:

Answer:

A Sink

Explanation:

Anything greater than 1g/cm3 will sink in water

Matter are anything that is made up of atoms. The quantity of matter can be observed only on the basis of mass and volume calculation. Therefore, loosing and gaining energy by different phase of water, phases changes.

Matter is a substance that has some mass and can occupy some volume. The matter is mainly used in science. Matter can be solid, liquid or gas.

Matter is anything that is made up of atoms. Anything around us that can be physically seen and touched are matter. Ice, water and water vapors are example of matter.

When water particles in their gaseous state (X) lose enough energy, then the gaseous state of water converts to liquid state as the kinetic energy of particles decreases. When water particles in their liquid state (Y) gain enough energy, then water converts to vapor state.

Therefore,  loosing and gaining energy by different phase of water, phases changes.

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Answer:

D

Explanation:

The pineal gland regulates salt and water levels.

The pineal gland does not regulate salt and water levels. Therefore, option (D) is correct.

The pineal gland can be described as a pinecone-shaped small gland located in the middle of the human brain. The pineal gland is the main site for melatonin secretion, which regulates the internal clock of the body.

The dimensions of the pineal gland can be described as about 0.3 inches long and weighing 0.1 grams. The pineal gland is made of pinealocytes and supporting cells that are similar to the astrocytes in the brain.

The pineal gland secretes the hormone melatonin and this hormone regulates the circadian rhythm of the body and also reproductive hormones. The secretion of hormones depends upon the quantity of light a person is exposed to.

This hormone is formed in huge amounts when it is dark. The presence of light prevents the secretion of melatonin which controls circadian rhythms.

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Answer:

A. atomic number

Explanation:

An atomic number of the elements increases as you move across a period from left to right. Hence, option A is correct.

An atomic number is the number of a chemical element in the periodic system, whereby the elements are arranged in order of increasing the number of protons in the nucleus.

In a period atomic number increases as we move from left to right but the outermost shell remains the same. Hence it's only the number of protons increasing in the nucleus as we from left to right, the effect of the nucleus increases on the outermost shell hence atomic size decreases in a period.

Hence, The atomic number of the elements increases as you move across a period from left to right.

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Answer:

Explanation:

Symbol: K

Protons = 19

Electrons in an atom: 19

Neutrons: 39 - 19 = 20

Draw the nucleus at the center. Label it with 19 Protons and 20 Neutrons.

Draw a circle around the nucleus.

Put two dots opposite each other on the circle's circumference.

Draw another circle with its center at the nucleus bigger than you first circle.

Space 8 electrons around the circumference.

Draw a third circle like the other 2 only bigger.

Space 8 electrons around this circle's circumference.

Draw 1 more circle bigger than the third circle.

It has 1 electron.

Answer:

1 = Melting

2 = Freezing

3 = Sublimation

4 = Deposition

5 = Condensation

6 = Boiling

Explanation:

Answer:

tetrafluoroethane

Explanation:

Its an HCFC, which are the refrigerants that destroy the ozone layer.

Answer:

Freon.

Explanation:

Brainliest plz???

Answer:

hiiiiiiiiiiiiiiiiiiiiiiiiiiii

Answer:

The name of this unit in the measurement is called: Liter

Answer:

See attached picture.

Explanation:

Hello.

In this case, since butane has two common occurring structures, n-butane and isobutane, there is a way in which the tert-butyl radical can be formed upon the removal of a hydrogen from the isobutane form of butane as shown on the attached picture, wherein you can see that the radical is named by "tert" since the central carbon is bonded to three carbon atoms, that is why we classify it as tertiary. Moreover, it is a radical due to the presence of the bolded dot next to the tertiary carbon suggesting that it is very likely to bond with an other atom.

Best regards.

Answer:

A typical atom consists of three subatomic particles: protons, neutrons, and electrons (as seen in the helium atom below). Other particles exist as well, such as alpha and beta particles (which are discussed below). The Bohr model shows the three basic subatomic particles in a simple manner. Most of an atom's mass is in the nucleus—a small, dense area at the center of every atom, composed of nucleons. Nucleons include protons and neutrons. All the positive charge of an atom is contained in the nucleus, and originates from the protons. Neutrons are neutrally-charged. Electrons, which are negatively-charged, are located outside of the nucleus.

Explanation:

The answer is A) Quantitative because Carrie has collected actual data and has not just made a judgement or prediction.

Hope this helps! :)

Answer:

of different elements with different electronegativities

Explanation:

A molecule containing two atoms "of different elements with different electronegativities"

A polar covalent bond exists when two different atoms (non-metals) with different electronegativities are able to share their electrons in a covalent bond.

Some examples of polar covalent bonds are seen in:

1. Ammonia(NH3): The polar covalent bonds exists between the nitrogen and hydrogen atoms.

2. Water(H2O): The polar covalent bond exists between hydrogen and oxygen. The oxygen molecule has a net negative charge while the hydrogen atoms have a net positive charge.

Answer:

[tex]MgCl_2+2NaOH\rightarrow 2NaCl+Mg(OH)_2[/tex]

Explanation:

Hello.

In this case, since aqueous magnesium chloride reacts with aqueous sodium hydroxide, a precipitate product, magnesium hydroxide is formed as well as aqueous sodium chloride as shown below:

[tex]MgCl_2+NaOH\rightarrow NaCl+Mg(OH)_2[/tex]

However, since there are two chlorine atoms at the reactants we need a 2 before NaCl on the products in order to balance it. Moreover, there one OH at the  reactants and two OH at the products, that is why we also add a 2 before NaCl as shown below:

[tex]MgCl_2+2NaOH\rightarrow 2NaCl+Mg(OH)_2[/tex]

Best regards!

Answer:

Explanation:

I think that it is frequency

Answer:

B

Explanation:

Answer:

i)   0.5071 (kg/s)

ii)  -1407.1 kj/kg

iii)  204.05 Kw

iv)  5.881

v)    9.238

Explanation:

Given Data:

evaporation temperature ( T ) = 4°c = 277.15 K

Condensation Temperature ( T ) = 34°c = 307.15 K

n ( compressor efficiency ) = 0.76

refrigeration rate = 1200 kJ.s^-1

i) determine the circulation rate of the refrigerant

m = [tex]\frac{Q}{H2 - H1}[/tex]  = [tex]\frac{Q}{H2 - H4\\}[/tex]  ------- 1

Q = 1200 Kj.s^-1

H2 = entropy at step 2 = 2508.9 (kJ / kg ) ( gotten from Table F )

H4 = entropy at step 4 = 142.4 ( kJ/ kg )

back to equation 1

m ( circulation rate of refrigerant ) = 0.5071 (kg/s)

ii) heat transfer rate in the condenser

Q = m ( H4 - H3 )

    = 0.5071 ( 142.4 - 2911.27 )

    = -1407.1 kj/kg

where H3 = H2 + ΔH23 = 2911.27 (kj/kg) ( as calculated )

iii) power requirement

w = m * ΔH23

   = 0.5071 (kg/s) * 402.37 (kj/kg) =  204.05 Kw

where: ΔH23 = [tex]\frac{H'3 - H2 }{0.76}[/tex] = [tex]\frac{2814.7-2508.9}{0.76}[/tex] = 402.37 (kj/kg)

iv) coefficient of performance of a cycle

W = Qc / w

  = 1200 Kj.s^-1/ 204.05 kw

  = 5.881

v) coefficient of performance of a Carnot refrigeration cycle

[tex]w_{carnot} = \frac{T2}{T4 - T2}[/tex]

            =  277.15 / ( 307.15 - 277.15 )

            = 9.238