Human lungs have evolved to breathe oxygen at a pressure as that in the atmosphere, 0.21 atm. If a particular heliox mixture to be carried by a scuba diver is at a pressure of 7.00 atm, what should be the partial pressure due to helium in order to maintain the pressure due to oxygen at 0.21 atm?

Answer:

1.Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.

2.The scientific method is an empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century. It involves careful observation, applying rigorous skepticism about what is observed, given that cognitive assumptions can distort how one interprets the observations.

Answer: answer is C

Explanation:

Its product is heavier than each of its reactants is true about this ₇N¹⁴ + ₁H¹ →  ₈O¹⁵ reaction

A nuclear reaction is a reaction in which one or more than one nuclides are generate and it collides between two atomic nuclei or one atomic nucleus.

The reaction is  

₇N¹⁴ + ₁H¹ →  ₈O¹⁵

Now equating the mass number of both sides

14 + 1 = 15 + a

a = 0

Equating atomic number of both sides

7 + 1 = 8 + x

x = 0

Thus, we can say that its product is heavier than each of its reactants is true about this reaction

Hence, option C is correct answer.

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Answer:

The particles of frosting absorbed energy from their surroundings and changed from the solid to the liquid state.

Explanation:

On a sunny day, the energy of the particles in the surrounding is higher than the energy of the frosting tray of cupcakes.

As a result of the exchange of energy between the tray of cupcakes and the surrounding, the tray of cupcakes absorbs energy from the surrounding. When this occurs, the firm frosting is now converted from solid to liquid which is runny and wet to touch, hence the answer above.

Answer:

A few of the positive particles aimed at a gold foil seemed to bounce back.

Explanation:

Rutherford's experiment took the search for the structure of the atom a step further. In this experiment, a narrow beam of alpha particles emitted from a source was used to bombard a thin gold foil.

The scattering of the alpha particles was detected by a movable ZnS screen. It was found that most of the alpha particles followed a straight path through the gold foil but some were scattered through large angles and some even scattered backwards.

Following this experiment, Rutherford decided on his planetary model of the atom in which the nucleus is at the core of the atom with electrons moving round the nucleus in orbits. Rutherford was awarded a Nobel prize for this work.

Answer:

a

Explanation:

edge 2020

Answer:

The solution formed is called Barium hydroxide Ba(OH)2 and metal A is Barium

Explanation:

All basic oxides except BaO are insoluble in water

Answer:

Explanation:

The glass (which does not crystallize even though it is accepted) of a window is NOT a mineral, since it is neither a substance of natural origin (although it is manufactured from natural components) nor does it have a defined crystalline structure, that is, the atoms they are not arranged in an orderly and regular way along axes and planes forming flat faces that keep a symmetry.

Remember that a mineral is defined as a solid, inorganic, homogeneous substance, of natural origin, with a crystalline structure and a determined and well-defined chemical composition within narrow margins and that has regular and characteristic physical properties.

Explanation: No, glass is not a mineral. ... Definable chemical composition: SiO2 *Actually, most industrially-produced glass is not pure silica, but having impurities is still a definable chemical composition so this part of the definition is ok. Orderly arrangement of atoms in a lattice: NO.

Answer:

+2

Explanation:

Oxidation number of an element, also called its oxidation state, is the number of electrons its atoms lost or gain in the process of forming a chemical compound.

To determine the oxidation state of an element or compound;

- The sum of all the oxidation numbers in a neutral compound must equal zero (0).

In the compound: Fe2(CO3)2

This compound is a neutral one, hence, its oxidation state is equal to zero (0).

It contains a polyatomic ion (carbonate ion) i.e. CO3 2-, whose net charge is -2.

Hence, to find the oxidation number of Iron (Fe), which is represented by X, in the compound, we say;

X(2) + -2(2) = 0

2X + -4 = 0

2X - 4 = 0

2X = 4

X = +2

Therefore, the oxidation number of Fe in Fe2(CO3)2 is (+2)

The compound Fe2(CO3)2 is called Iron (II) carbonate

Oxidation number of Fe in [tex]\rm Fe_2(CO_3)_2[/tex] is 2. An atom's oxidation number is a positive or negative number.

A notion used in chemistry to characterise the relative electron distribution and the level of oxidation or reduction of atoms in a compound or ion is known as the "oxidation number," sometimes known as the "oxidation state." Based on the presumption that electrons in chemical bonds are entirely transmitted to the more electronegative atom, it is a method of bookkeeping that assigns a notional charge to each individual atom in a molecule or ion.

The -4 stands for the overall charge that the carbonate ions provided, and the x is the Fe's oxidation number.

2x + (-4) = 0

2x - 4 = 0

2x = 4

x = 4/2

x = 2

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Answer is D

Explanation:

Answer:

B. Neutral

Explanation:

When there is a ionic bond,  one element steals or takes away an electron from the other element.

An example is NaCl

In this compound, Chlorine atom steals an extra electron from Sodium to fill its outer shell. So, this is a Ionic bond. Since, the Sodium compound gives away an atom, it is positively charged. Since, Chlorine steals an atom, it is negatively charged. Opposite charges attract, so they become a compound.

When positive and negative mix, it becomes neutral.

Answer:

Explanation:

[tex]Move \: the\:decimal \:point\:,\\3 \:times\:to\:the \:right = 24\\\\When \:the\:decimal\:point \: moves\\\:to\:the \:right\:it\:becomes\:a \:negative\:power\\\\0.024= 24 \times 10^-^3[/tex]

Answer:

When you are going to measure small lengths or objects or when you are going to measure things with great accuracy.

Explanation:

Answer:

The mass of NH₃ left over = 0.91 g of NH₃

The mass of H₂ left over = 8.2 g of H₂

Explanation:

The given information are;

The mass of the carbon monoxide present in the reaction = 25.0 g

The mass of the ammonia present in the reaction = 8.50 g

The mass of the hydrogen present in the reaction = 10.0 g

The above masses reacts to produce water and acetonitrile (CH₃CN)

The balanced chemical equation for the reaction is given as follows;

2CO + NH₃ + 2H₂ → CH₃CN + 2H₂O

Therefore, two moles of CO reacts with one mole of NH₃ and  two moles of H₂ to produce one mole of CH₃CN and two moles of H₂O

The molar mass of CO = 28.01 g/mol

The molar mass of NH₃ = 17.031 g/mol

The molar mass of H₂ = 2.0159 g/mol

The molar mass of H₂O = 18.015 g/mol

The molar mass of CH₃CN = 41.05 g/mol

The number of moles of CO present = 25/28.01 = 0.893 moles

The number of moles of NH₃ present = 8.5/17.031 = 0.5 moles

The number of moles of H₂ present = 10/2.0159 = 4.96 moles

Therefore, 0.893 moles of CO reacts with 0.893/2 mole of NH₃ and  0.893 moles of H₂ to produce 0.893/2 mole of CH₃CN and 0.893 moles of H₂O

The excess reactants left are;

0.5 - 0.893/2 = 0.0535 moles of NH₃ with mass 0.0535 × 17.031 = 0.91 g

4.96 - 0.893 = 4.067 moles of H₂ with mass 4.067 × 2.0159 = 8.2 g

The mass of NH₃ left over = 0.91 g of NH₃

The mass of H₂ left over = 8.2 g of H₂.

Answer:

inter atomic bonds

Explanation:

because it is loosely held

Answer:

[tex]4.85 * 10^4\ mL[/tex]

Explanation:

Given

485 L

Required

Determine the measurement not equal to 485L

[tex]0.485\ kL[/tex]

From standard unit of conversion;

1 KL = 1000 L

Multiply both sides by 485

[tex]485 * 1 KL = 485 * 1000 L[/tex]

[tex]485KL = 485000L[/tex]

Divide both sides by 1000

[tex]\frac{485KL}{1000} = \frac{485000L}{1000}[/tex]

[tex]0.485KL = 485L[/tex]  ---- This is equivalent

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

[tex]4.85 * 10^4\ mL[/tex]

From standard unit of conversion;

1000 mL = 1 L

Multiply both sides by 485

[tex]485 * 1000 mL = 1 L * 485[/tex]

[tex]485000\ mL = 485\ L[/tex]

Convert to standard form

[tex]4.85 * 10^5\ mL = 485\ L[/tex]

Hence; [tex]4.85 * 10^4\ mL[/tex] is not equivalent to 485L

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

[tex]48500 \ cL[/tex]

From standard unit of conversion;

100 cL = 1 L

Multiply both sides by 485

[tex]485 * 100 cL = 1 L * 485[/tex]

[tex]48500\ cL = 485\ L[/tex]

Convert to standard form

[tex]4.85 * 10^4\ cL = 485\ L[/tex] ---- This is equivalent

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

[tex]4.85 * 10^8 \[/tex] μL

From standard unit of conversion;

1000000 μL = 1 L

Multiply both sides by 485

[tex]485 * 1000000uL = 1 L * 485[/tex]

[tex]485000000uL = 485\ L[/tex]

Convert to standard form

[tex]4.85 * 10^8\ uL = 485\ L[/tex] ---- This is equivalent

From the list of given options;

[tex]4.85 * 10^4\ mL[/tex] is not equivalent to 485L

Answer:

materials which do not show the quality of lustre i.e. shiney surface

for eg- non metals except Iodine

Explanation:

hope it helps u plz mark as the brainliest

Answer:

These are materials that don't have lustre

Explanation:

They are not shiny.

They include non-metals but not iodine.

Hope it helps.

Answer:

C. 1 cubic foot of loose sand

Explanation:

For many  objects having equal volume , surface area will be maximum

of the object which has spherical shape .

But when a sphere is broken into tiny small spheres , total surface area of all the small spheres will be more than surface area of big sphere .

Hence among the given option , surface area of loose sand will have greatest surface area . Loose sand is equivalent to small spheres .

Answer:

the answer would be C 1 cubic foot of loose sand.

Answer:

Fórmula empírica: C₂H₂N

Fórmula molecular: C₄H₄N₂

Explanation:

Un compuesto que contiene carbono hidrógeno y nitrógeno con fórmula CₐHₓNₙ es sometido a combustion produciendo:

CₐHₓNₙ + O₂ → aCO₂ + x/2 H₂O + nNO₂

Con la masa de dióxido de carbono y agua podemos encontrar las moles de carbono e hidrógeno y su aporte a los 0.452g de muestra que fueron puestos en combustión, así:

Moles C:

Moles C = Moles CO₂ = 0.994g CO₂ ₓ (1mol / 44g) = 0.0226 moles C

Masa C: 0.0226 moles C ₓ (12.01g / mol) = 0.271g Carbono hay en la muestra

Moles H:

Moles H = 2 Moles H₂O = 0.203g H₂O ₓ (1mol / 18g) = 0.0113 moles H₂O = 0.0226 moles H

Masa H: 0.0226 moles H ₓ (1.01g / mol) = 0.023g Hidrógeno hay en la muestra

Así, la masa de nitrógeno en la muestra y sus moles son:

Masa N = 0.452g - 0.271g C - 0.023g H

Masa N = 0.158g Nitrógeno

Y su moles son:

0.158g ₓ (1 mol / 14.01g) = 0.0113 moles N

Con las moles de C, H y N podemos determinar la formula empírica que se define como: "La relación de números enteros más simple entre la cantidad de átomos presentes en una mólecula. Si usamos como base las moles de nitrógeno (Valor menor):

Relación H/N: 0.0226 mol / 0.0113 mol = 2

Relación C/N: 0.0226 mol / 0.0113 mol = 2

Relación N/N: 0.0113 mol / 0.0113 mol = 1

Así, la fórmula empírica es:

Esta fórmula empírica tiene una masa molar de:

2C = 2*12 g/mol = 24g/mol

2H = 2*1g/mol = 2g/mol

N = 14g/mol

24+14+2 = 40g/mol

Como la masa molecular del compuesto es 80g/mol (Dos veces la de la fórmula empírica, la fórmula molecular es 2 veces la fórmula empírica:

Answer:

-Over time, the rates of the forward and reverse reactions equalize.

-Initially, the concentration of products is low, so the rate of the reverse reaction is also low.

Explanation:

A chemical reaction is said to be reversible when the reactants forms the products, which in turn reacts together again to give rise to the reactants. In a reversible reaction, the formation of products from reactants occurs simultaneously with the reformation of the reactants from the products. For example:

The reversible reaction: A + B ⇆ C + D means;

A + B → C + D and C + D → A + B

The rate at which both forward and reverse reactions are taking place in closed system may be initially different but with time, it gets equal to form an equilibrium reaction. However, at first, only the rate of the forward reaction proceeds because the concentration of the product is low. Hence, the rate of reaction of the reverse reaction (product to reactants) is low as well.

In the reversible reaction above, the rate of the reverse reaction (C + D → A + B) will turn out low initially because the concentration of the products (C and D) are low. With time, the rates of the forward and reverse reaction becomes equal to form an EQUILIBRIUM or STABLE reaction.

Answer:

See explanation

Explanation:

The wittig reaction is an organic reaction in which an aldehyde or a ketone reacts with a phosphonium ylide to give an alkene. This phoshonium ylide that participates in the reaction is usually generated insitu in the system by reaction of an alky or aryl triphenylphosphonium halide salt with a base(sodium hydroxide is mostly used).

In this particular reaction 4-methylbenzaldehyde and benzyltriphenylphosphonium chloride were reacted together in the presence of sodium hydroxide and the product with the structure shown in the answer was obtained as the major isomer produced in the reaction.

Answer:

1) The volume occupied by an atom is composed of mainly empty space

2) Atoms have a very small, relatively dense, central nucleus that is positively charged

3) The region around the nucleus of an atom are orbited by negatively charged electrons in a the same fashion planets orbit around the Sun.

Explanation:

The selection of gold for the gold foil experiment was due to its ability to be rolled into extremely thin sheets such that it was expected for alpha particle to perforate or pass through the foil.

Answer:

[tex]\Large \boxed{\mathrm{A}}[/tex]

Explanation:

Rust formed from iron and oxygen combining is a chemical change, because in a chemical change, the resulting substance(s) will have different properties from the substance(s) before the chemical change.

I cant comment... So is it Right?

Answer:

The atomic number of the atom is 14.

Explanation:

The following data were obtained from the question:

Valence electrons = 4

Atomic number =.?

From the question given, we were told that the valence electron is in the m shell. Thus, we can say:

M shell = 4 electrons

The number of shells of the atom can be written in the order K, L, M with M as the last shell because we were told that the valence electrons i.e electrons in the outer shell is located at the M shell.

From a detailed knowledge of atom,

K shell = 1st shell

L shell = 2nd shell

M shell = 3rd shell

The first shell, K of an atom can only accommodate 2 electrons while others can accommodate a maximum of 8 electrons.

Note: we can only put electrons in another shell if a shell is already having 8 electrons. This rule only applies to the 2nd shell and above.

Thus, the atom in question has the following electrons:

K shell = 1st shell = 2 electrons

L shell = 2nd shell = 8 electrons

M shell = 3rd shell = 4 electrons

To get the atomic number of the atoms, we simply add all the electrons together.

This is illustrated below:

Atomic number = 2 + 8 + 4

Atomic number = 14

Therefore, the atomic number of the atom is 14.

Answer:

The answer on Edge is,

C. the number of valence electrons an atom has

Answer:

conclusion

Explanation:

it can't be a hypothesis since tests are carried out to verify so it is not a theory

an introduction to an experiment only gives the basis of what we are investigating therefore nothing has been proven and the question is still unanswered

The overall takeaway of an experiment’s results is the conclusion. Hence, option C is correct.

A hypothesis is a testable statement about the relationship between two or more variables or a proposed explanation for some observed experiment.

The overall takeaway of an experiment’s results can't be a hypothesis since tests are carried out to verify so it is not a theory

An experiment only gives an idea about the investigation therefore nothing has been proven and the question is still unanswered.

Hence, the overall takeaway of an experiment’s results is the conclusion.

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Answer:

Rubbing your hands together converts mechanical energy to thermal energy. Turning on a light switch converts mechanical energy to electrical and radiant energy.

Answer:

1. Metal.

2. Atom.

3. Homogeneous

4. Compounds.

5. Lustrous

6. Saturated.

7. Colloidal; true.

8. Homogeneous.

Explanation:

1. An element which are sonorous are called metal.

2. An element is made up of only one kind of atom.

3. Alloys are homogeneous mixtures.

4. Elements chemically combines in fixed proportion to form compounds.

5. Metals are lustrous and can be polished.

6. A solution in which no more solute can be dissolved is called a saturated solution.

7. Milk is a colloidal solution but vinegar is a true solution.

8. A solution is a homogeneous mixture.

Answer:

Heat of sublimation of Li(s) = 160.5 kJ/mol

Explanation:

Given that:

[tex]\mathtt{2Li(s) + \dfrac{1}{2} I_2(g) \to 2LiI(s)}[/tex]

ΔH = –292 kJ

The heat of formation for the above reaction =  –292 kJ × 2 =  -584 kJ/mol

[tex]\mathtt{Li^+_{(g)} + I^-_{(g)} \to LiI_{(s)}}[/tex]

The lattice energy of LiI(s) = -753 kJ/mol

[tex]\mathtt{Li(g)\to Li^+(g) + e^- }[/tex]

The ionization energy of LiI(s) = +520 kJ/mol

[tex]\mathtt{I_2_{(g)} \to 2I_{(g)} }[/tex]

The Bond Energy of I₂(g) = 151 kJ/mol

[tex]\mathtt{I_{(g)} + e^- \to I^-_{(g)}}[/tex]

The electron affinity of I(g) = -295 kJ/mol

Heat of sublimation: Sublimation is the process of changing of a solid matter into gas without passing through the liquid stage, Now, the molar heat of sublimation is the amount of energy that must be added to a mole of solid  to turn it directly into a gas without any interference through the liquid phase provided the pressure is  constant.

From  the above reactions: The heat of sublimation  of Li(s) can be calculated by the sum total of the following.

[tex]\mathtt{Li_{(s)} + \dfrac{1}{2} I_2_{(g)} \to LiI_{(s)} \ \ -292 kJ/mol} \\ \\\mathtt{I_{(g)} \to \dfrac{1}{2} I2(g) \ \ -75.5 kJ/mol} \\ \\ \mathtt{I^-(g) \to I(g) + e^- \ \ +295 kJ/mol} \\ \\ \mathtt{LiI(s) \to Li^+_{(g)} + I^-_{(g)} \ \ +753 kJ/mol} \\ \\ \mathtt{Li^+_{(g)} + e^- \to Li(s) \ \ -520 kJ/mol} \\ \\[/tex]

[tex]\mathtt{Li(s) \to Li(g)}[/tex] = (-292 +(-75.5)+295+753+(-520)) kJ/mol

[tex]\mathtt{Li(s) \to Li(g)}[/tex] =  160.5 kJ/mol

Heat of sublimation of Li(s) = 160.5 kJ/mol

Answer:

≈ 0.104 liters  

Explanation:

We can use Boyle's Law: [tex]P_{1}V_{1} = P_{2}V_{2}[/tex]

P₁ = 2.50 atm

V₁ = 25.0 mL

P₂ = 457 mmHg

V₂ = ?

Because pressure should be in atm we will convert 457 mmHg to units in atm:

1 atm = 760mmHg so we can divide 457 by 760 and we get ≈ 0.601atm

Next we can plug in the units to the equation for Boyle's Law:

(2.50)(25.0) = (0.601)(V₂)

Solve for V₂

V₂ will give you ≈ 104mL or 0.104L

Either is correct depending on which unit they are asking you to use

Answer:

The system will shift to the left producing more moles of gases trying to maintain the original pressure of the system

Explanation:

Based on LeChatelier's principle, a change in temperature, pressure, volume or concentration on a system result in an opposing change trying to maintain the initial equilibrium conditions.

In the reaction:

N₂(g) + 3H₂(g) ⇄ 2NH₃(g)

4 moles of gas reacts producing 2 moles of gas.

In a gas reaction, the system will try to maintain the total pressure.

If the volume of the container increases, the system will shift to the side of the reaction that has more moles of gases in order to maintain the pressure.

That means if in the reaction the volume of the container increase from 2.0L to 4.0L the system will shift to the left producing more moles of gases trying to maintain the original pressure of the system.

Answer:

The water cycle or hydrologic is a continuous cycle where water evaporates, travels into the air and becomes part of a cloud, falls down to earth as precipitation, and then evaporates again. This repeats again and again in a never-ending cycle. Water keeps moving and changing from a solid to a liquid to a gas, over and over again.

Precipitation creates runoff that travels over the ground surface and helps to fill lakes and rivers. It also percolates or moves downward through openings in the soil to replenish aquifers under the ground. Some places receive more precipitation than others do. These areas are usually close to oceans or large bodies of water that allow more water to evaporate and form clouds. Other areas receive less precipitation. Often these areas are far from water or near mountains. As clouds move up and over mountains, the water vapor condenses to form precipitation and freezes. Snow falls on the peaks.

The continual movement of water on, above, and below the Earth's surface is referred to as the water cycle, also known as the hydrological cycle.

The water cycle demonstrates how water is constantly moving both inside the Earth and in the atmosphere. It is a complicated system with a wide range of processes.

Water vapor is created when liquid water evaporates, and this water vapor then condenses to form clouds and falls back to earth as rain and snow.

The constant flow of water between the ground and the atmosphere is known as the water cycle. Water travels to land as precipitation, like snow and rain.

The cycle is then completed by the water evaporating, condensing into clouds in the atmosphere, and precipitating once more on earth. The water cycle is composed mostly of four processes: evaporation, convection, precipitation, and collection.

Thus, The continual movement of water on, above, and below the Earth's surface is referred to as the water cycle.

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