How did early chemists determine which substances were elements?

a. By observing chemical reactions

b. By finding the atomic mass

c. By counting neutrons

d. By counting protons

It would be A, Petroleum.

Hope this helped!

-William

Answer:

Its C

Explanation:

Ok. You really know how.

Answer:

the answer would be b

Explanation:

Atoms exchange or share electrons during bonding to obtain stability by completing their valence shells and also to achieve a lower energy state.

Atoms exchange or share electrons during bonding because of the force of attraction between two oppositely charged ions or particles called the electrostatic force. This force of attraction results in the formation of a bond, holding two atoms together within a compound.

The electrons are either shared or exchanged because they determine the chemical reactivity of an atom and are responsible for forming bonds between atoms. Atoms bond with each other to complete their outer shells and obtain stability, which is usually achieved by acquiring eight electrons in their valence shells. This is known as the octet rule.

The main types of chemical bonds that atoms form include covalent bonds and ionic bonds. Covalent bonds involve the sharing of electrons between atoms, while ionic bonds involve the transfer of electrons from one atom to another. Ionic bonding occurs between atoms that have a large difference in electronegativity, whereas covalent bonding occurs between atoms with a small difference in electronegativity.

In conclusion, atoms exchange or share electrons during bonding to obtain stability by completing their valence shells and also to achieve a lower energy state.

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a) To calculate the pH of distilled water, we can use the formula: pH = -log[H+].

Given that the [H+] concentration of distilled water is 10^-10 H mol/L, we can substitute this value into the equation:

pH = -log(10^-10) = 10

Therefore, the pH of distilled water is 10.

b) Tap water with a pH between 6.3 and 6.6 is less acidic than distilled water. The pH scale is logarithmic, meaning that each unit change represents a tenfold difference in acidity or alkalinity. Distilled water with a pH of 10 has a higher concentration of hydroxide ions (OH-) compared to hydrogen ions (H+), indicating it is basic or alkaline.

Tap water with a pH range of 6.3 to 6.6 indicates a higher concentration of hydrogen ions (H+), making it slightly acidic. Although both distilled water and tap water have a pH below 7, tap water is closer to neutral (pH 7) and thus less acidic than distilled water.

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The compound with the lower lattice energy is sodium fluoride (NaF). The lattice energy of a compound is a measure of the strength of the bonds between its ions.

The lattice energy of NaF is lower than that of NaCl because the sodium ion has a greater charge-to-radius ratio, so the attraction between the oppositely-charged ions is stronger.

In contrast, the potassium ion has a lower charge-to-radius ratio, so the attraction between the two potassium ions in K2O is weaker than that in K2S.

Therefore, the lattice energy of K2O is lower than that of K2S. In conclusion, NaF has the lower lattice energy of the two compounds given.

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In order for electrolysis to take place, a salt such as Na2SO4 is required. It makes available the ions Na+ and SO42, both of which are drawn to the electrodes in the solution and move toward them as a result. They do not experience a discharge when brought close to the electrodes. However, they are able to cancel out the electric charges carried by the ions that are formed as a result of the destruction of water by these electrodes. Let's check out what's happening at each of the electrodes.

At the cathode, often known as the negative pole, water breaks down in the following manner:

2H2O+2e−⟶H2+2OH−.This is only conceivable if some positive ions are available near the cathode to compensate for the negative charges emerging in the solution with these freshly produced OH ions. The only way this can happen is if there are some positive ions available near the cathode. In the absence of positive ions, such as Na+, in the vicinity of the cathode, the newly formed OH ions would function as a barrier to subsequent electrons coming from the external circuit, preventing those electrons from reaching the electrode and preventing the electrode from interacting with water. The electrolysis would come to a halt as a result.

At the anode, often known as the positive pole, the following reactions take place in water:

4H2O⟶O2+4H++4e− .This is only conceivable if there are negative ions coming near the anode to compensate for the positive charges that are forming in the solution as a result of these freshly produced H+ ions. A positively charged solution would result if the solution near the anode did not include any negative ions, such as SO42. Instead, the solution would contain the new H+ ions. This would stop any further electrons from being released from the water as a result. The electrolysis would come to a halt as a result.

The process culminates in a transformation of the solution's chemical makeup near the electrodes. When you go closer to the cathode, you'll notice that the solution has a higher concentration of NaOH. In the vicinity of the anode, the solution includes an increasing amount of H2SO4. Naturally, if you agitate and combine solutions that are anodic and cathodic, the acid and the base will neutralize each other, which will result in the solution being regenerated to contain the initial salt.

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The chemical equation for O2 binding to haemoglobin to form oxyhemoglobin can be written as follows:

Hb + 4O2 ⇌ Hb(O2)4

In this equation, Hb represents hemoglobin, which is a protein found in red blood cells that is responsible for binding to oxygen and transporting it throughout the body. O2 represents oxygen molecules that are present in the surrounding environment. When these oxygen molecules come into contact with haemoglobin, they bind to it to form oxyhaemoglobin, which is a bright red-colored compound.

The reaction is reversible, meaning that oxyhemoglobin can release the oxygen molecules when it reaches the tissues in the body that require oxygen. This process is facilitated by changes in the shape of the haemoglobin molecule, which are triggered by factors such as changes in pH, temperature, and carbon dioxide levels.

Overall, the binding of oxygen to hemoglobin is a critical process that ensures that oxygen is efficiently transported to the tissues in the body where it is needed for cellular respiration and energy production.

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The thermometer will read -10°C after about 2.43 minutes.

(a) After four more minutes, the thermometer will read -1°C.

This is because the temperature difference between the room and outdoors is (24 - (-11)) = 35°C.

The thermometer then rises 7°C in one minute, so the thermometer is heated at 7°C/minute, i.e. 35°C in five minutes.

So the temperature of the thermometer after 4 more minutes is 7°C + 7°C + 7°C + 7°C = 28°C, 28°C - 35°C = -7°C, -7°C - 3°C = -10°C.

Thus the reading on the thermometer will be -1°C after four more minutes.

(b) To find out when the thermometer will read -10°C, use the formula:

time = (temperature difference ÷ heating rate) + time to start

       = (-10°C - 7°C) ÷ 7°C/minute + 1 minute

       = -17°C ÷ 7°C/minute + 1 minute≈ -2.43 minutes

Thus, the thermometer will read -10°C after about 2.43 minutes.

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Answer:

evaporation means the state of the water went from liquid to gas which is a physical change. the sugar is still in the beaker which means its chemical properties did not change.

Explanation:

Therefore, the concentration of the H₃PO₄ solution is 0.839 mol/L or 0.839 M.

Phosphoric acid (H₃PO₄) has three dissociable protons and therefore can undergo three successive acid-base reactions with NaOH. Each reaction produces a different amount of moles of NaOH, depending on the number of protons dissociated.

At the third equivalence point, all three protons have reacted with NaOH and the moles of NaOH added are equal to the moles of H₃PO₄ present in the original solution.

The balanced equation for the reaction between NaOH and H₃PO₄ is:

H₃PO₄ + 3 NaOH → Na₃PO₄ + 3 H₂O

We can use the balanced equation and the volumes and molarity of the NaOH solution to calculate the moles of NaOH added:

moles of NaOH = Molarity x Volume in liters

moles of NaOH = 1.25 mol/L x 0.0262 L

moles of NaOH = 0.03275 mol

Since the titration is at the third equivalence point, the moles of NaOH added are equal to the moles of H₃PO₄ present in the original solution. Therefore:

moles of H₃PO₄ = 0.03275 mol

To calculate the concentration of the H₃PO₄ solution, we need to divide the moles of H₃PO₄ by the volume of the sample used in the titration, in liters:

concentration of H₃PO₄ = moles of H₃PO₄ / volume of sample in liters

concentration of H₃PO₄ = 0.03275 mol / 0.0390 L

concentration of H₃PO₄ = 0.839 mol/L

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Time taken for star to reach Earth = 7.5 years

Given

7.5 light years(distance Earth-star)

Required

Time taken

Solution

Speed of light=v = 3 x 10⁸ m/s

1 light years = 9.461 × 10¹⁵ m= distance(d)

So time taken for 1 light years :

time(t) = distance(d) : speed(v)

t = 9.461 × 10¹⁵ m : 3 x 10⁸ m/s

t = 3.154 x 10⁷ s = 1 years

So for 7.5 light years, time taken = 7.5 years

Answer:

C. The initial version is tested during the third stage to determine what needs to be improved, and the beta version is tested during the fourth stage to ensure that criteria are met.

Explanation:

Edge 2021

The Testing of the initial version is carried out in the third stage to determine what needs to be improved, while the testing of the beta version is carried out during the fourth stage to ensure that all necessary criteria are met.

The process of technological design involves several distinctive processes which can be broken down into four stages.

The four stages involved in the  process of technological design are :

hence the testing of the initial version is to determine what needs improvement while the testing of the beta version is to ensure all criteria are met

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The equation related to reaction between Sulfur dioxide and oxygen to produce sulfur trioxide is 2SO\(_2\)(g) + O\(_2\)(g) \(\rightarrow\) 2SO\(_3\) (g).  SO\(_2\)  is limiting reagent.

The reactant that controls how much of the products are generated inside a chemical reaction is known as the limiting reagent. Since some of the other reactants remain that after limiting reagent has been used fully, it is occasionally discovered that they are in excess in the reactions. The theoretical yield is the most product that can theoretically be produced.

2SO\(_2\)(g) + O\(_2\)(g) \(\rightarrow\) 2SO\(_3\) (g)

moles of SO\(_2\) =20.0 g / 64.07

                      =0.312moles

moles of O\(_2\)= 15.6 g/32

                   =0.487moles

On dividing the moles by stoichiometry, out of  O\(_2\) and SO\(_2\), SO\(_2\)  is limiting reagent.

Therefore,  the equation related to reaction between Sulfur dioxide and oxygen to produce sulfur trioxide is 2SO\(_2\)(g) + O\(_2\)(g) \(\rightarrow\) 2SO\(_3\) (g).  SO\(_2\)  is limiting reagent.

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Answer:

The correct answer to the following question will be "1.76 g/L".

Explanation:

The given values are:

P₁ = 15 kPa

Solubility of water, C₁ = 0.66 g/L

P₂ = 40.0 kPa

C₂ = ?

Now,

According to Henry's Law,

⇒  \(\frac{P_{1}}{P_{2}}=\frac{C_{1}}{C_{2}}\)

⇒  \(C_{2}=\frac{C_{1}\times P_{2}}{P_{1}}\)

On putting the estimated values, we get

⇒       \(=\frac{0.66\times 40}{15}\)

⇒       \(=\frac{26.4}{15}\)

⇒       \(=1.76 \ g/L\)

When a metal dissolves in an acid such as hydrochloric acid (HCl), it undergoes a redox reaction where the metal atoms lose electrons to form positive ions while hydrogen ions from the acid gain electrons to form hydrogen gas. If a metal dissolves in HCl, it means that the metal atoms react with the hydrogen ions in the acid to form soluble metal chloride salts and hydrogen gas.

Aluminum (Al) dissolves in 1 M HCl because it is above hydrogen in the activity series of metals. The balanced redox reaction for the dissolution of Al is:
2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)
Silver (Ag) does not dissolve in 1 M HCl because it is below hydrogen in the activity series of metals. Therefore, it does not react with hydrogen ions from the acid. The balanced redox reaction for Ag not dissolving in HCl is:
Ag(s) + HCl(aq) → No reaction
Lead (Pb) dissolves in 1 M HCl because it is above hydrogen in the activity series of metals. The balanced redox reaction for the dissolution of Pb is:
Pb(s) + 2HCl(aq) → PbCl2(aq) + H2(g)
In summary, the dissolution of a metal in HCl depends on its position in the activity series of metals. If the metal is above hydrogen in the series, it will dissolve, and if it is below hydrogen, it will not dissolve.

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Answer: Synthesis (of phosphorous and oxygen to form tetraphosphorous decaoxide)

Explanation:

A tutorial concerning atomic orbitals can help one comprehend the fundamental tenets of quantum mechanics pertaining to atoms and their electrons.

This tutorial encompasses the shapes, extents, as well as energies of atomic orbitals; moreover, it shows how they congregate to create molecular orbitals.

In addition to that, it notifies us on how the electronic arrangements of atoms determine their chemical traits and functions such as responsiveness and its capability to bond with other atoms.

Thus, a tutorial concerning atomic orbitals builds up a foundation for understanding the behavior of matter at both the atomic and molecular levels.

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Note that the video was about Orbitals in Atoms. Here is some information about that.

Existence of electrons in an energy state is referred to as Basic Atomic Orbitals.

Characterized by their shape, energy, and probability of containing an electron, the orbitals are categorized into various types such as s, p, d and f - each with a unique structure and distinct energy levels. For instance, the spherical shape of an s-orbital possesses greater energy when away from the nucleus.

Meanwhile, a p-orbital has two lobes separated by a node. Of utmost importance when examining atoms, molecules, and chemical reactions is gaining knowledge about atomic orbitals. Unlike other orbitals, d and f varieties possess a high degree of complexity regarding shape as well as energy distribution.

Physically speaking,the probability that electrons exist within these orbitals can be determined through measuring electron densities based on their distances from nuclei.

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In a neutralization reaction, water is always formed. This is because a neutralization reaction involves the reaction of an acid and a base to form a salt and water.

The acid donates a hydrogen ion (H+) and the base donates a hydroxide ion (OH-) to form water (H+ + OH- -> H2O) and the remaining ions combine to form a salt. The salt formed depends on the specific acid and base used in the reaction. Therefore, the correct answer is: water.

Water is a transparent, colorless, odorless, and tasteless liquid that is essential for most forms of life. It is a chemical compound with the formula H2O, meaning it is made up of two hydrogen atoms and one oxygen atom, held together by covalent bonds.

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The amount of oxygen diffused in 1 hour under the steady state condition through a non diffusing gas mixture of methane is 0.14076 K mole/hr.m2. This is calculated using the expression of Molar flux.

The molar flux = \(DA_{M}\) * \(P_{t}\)* (\(P_{A1}\) - \(P_{A2}\)) / \(RTZP_{BM}\)

\(PB_{M}\) =(\(P_{B2}\)- \(P_{B1}\))/ ln (\(P_{B2}\)/ \(P_{B1}\))

\(P_{B2}\)= 105- 13*103   = 87*103  N/m2, \(P_{B2}\)= 105- 6500= 93.5*103 N/m2

\(PB_{M}\)=   (87*1000- 93.5*1000)/ ln (87/93.5)= 90200 N/m2

\(DA_{M}\)  =  Diffusivity of oxygen into mixture of  Methane and hydrogen

          =  (yCH4/\(DA_{B}\) + yH2/\(DA_{C}\))

Since  volume ratio of Methane to hydrogen is 2:1

y\(CH_{4}\)= 2/3 and y\(H_{2}\)= 1/3

\(DA_{B}\)= 1.86*10-5 m2/sec   and \(DA_{C}\) =  7*10-5 m2/sec

\(DA_{C}\)= 1/ (0.667/1.86*10-5+ 0.333/7*10-5) =2.462*10-5

\(N_{A}\) = 2.462*10-5*(13000-6500)/ 8314*273*0.002*90200

     =  3.91*10-5 K mole/m2.s

for 1  hour  NA= 3.91*10-5*3600 Kmolm2 =0.14076 K mole/hr.m2

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The correct question is,

calculate the amount of oxygen diffused in 1 hour under steady state conditions through a non-diffusing gas mixture of methane

Answer:

A,B,C,D

Explanation:

I just took the test

Answer:

Its

A: Multiply each donation amount by the number of people.

B: Add the total amount of money.

C: Add the total number of people.

D: 2,550 ÷ 25 = $102

Explanation:

Edg2020

Explanation:

Using a fractional column will help to separate liquids whit different boiling points since the mixture contain ethanol water and propanaol. Ethanol will be the first to be extracted since it has a low boiling point then it would be water and then propanaol.

The gas that does not bind to the porphyrin ring Fe (II) ion in myoglobin is option E) H2S. Myoglobin is a protein that is found in muscles and plays a crucial role in storing and transporting oxygen.

The heme group present in myoglobin contains an iron ion that is surrounded by a porphyrin ring. This iron ion is responsible for binding to oxygen and facilitating its transport. However, some gases like CO, NO, and O2 can also bind to this iron ion, which can have adverse effects on the body. Carbon monoxide CO and nitric oxide NO have a higher affinity for binding to the iron ion than oxygen, which can lead to oxygen deprivation in the body. In contrast, carbon dioxide CO2 can bind to a different site on the protein and assist in the release of oxygen. However, hydrogen sulfide H2S does not bind to the porphyrin ring Fe (II) ion in myoglobin and therefore does not interfere with oxygen transport.

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Answer:

It is broken down into water and oxygen

Explanation:

2H2O2 -----> 2H2O +O2

Answer: 86.14%, 100.86%

Explanation:

The relative atomic mass of an element is the average mass of the isotopes of the element, taking into account the abundance of each isotope. To determine the percentage abundance of each isotope, we can use the following formula:

Percentage abundance = (isotope mass / relative atomic mass) x 100

For the isotope with mass number 6, the percentage abundance would be:

(6 / 6.94) x 100 = 86.14%

For the isotope with mass number 7, the percentage abundance would be:

(7 / 6.94) x 100 = 100.86%

So the isotope with mass number 6 has an 86.14% abundance, and the isotope with mass number 7 has a 100.86% abundance. The sum of these two percentages is slightly greater than 100 because the relative atomic mass is an average and does not take into account the abundance of each isotope.

The maximum hardness obtained in a piece of steel is primarily determined by its carbon content. Steel is an alloy of iron and carbon, and the carbon atoms play a crucial role in influencing the material's hardness.

When steel is heated and then rapidly cooled in a process called quenching, the carbon atoms become trapped within the iron lattice structure. This rapid cooling prevents the carbon atoms from diffusing and forming larger crystals, resulting in a harder microstructure.

The higher the carbon content in the steel, the greater the potential for hardness. Steels with higher carbon concentrations can form more carbide particles, which contribute to increased hardness.

However, it's important to note that other factors can also affect the hardness of steel, such as the presence of other alloying elements (e.g., chromium, manganese) and the specific heat treatment processes employed. These factors can influence the formation of different microstructures and phases, affecting the steel's overall hardness.

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Answer:

energy from a source that is not depleted when used, such as wind or solar power.

Explanation:

Explanation:

renewable energy is energy from a source that is not depleted when used such as wind or solar power.

Hope this helps :)

Answer:

98 g/mol

Explanation:

atomic mass for hydrogen=1

atomic mass for sulphur=32

atomic mass for oxygen=16

atomic mass for sulphuric acid=2H + S + 4O

=2x1 + 32 + 4x16

2+32+64=34+64

=98g/mol