Can someone help? Thank you.

Trả lời:3 5-dimethylheptane

Explanation:

Answer:

The answer is "17200 years".

Explanation:

Given:

[tex]A = 20 \ \frac{counts}{minute}\\\\A_{o} = 160\ \frac{counts}{minute}[/tex]

Let the half-life of carbon-14, is beta emitter, is [tex]T = 5730\ years[/tex]

Constant decay [tex]\ w = \frac{0.693}{ T}[/tex]

[tex]= 1.209 \times 10^{-4} \ \frac{1}{year}\\[/tex]

The artifact age [tex]t= ?[/tex]

[tex]A = A_{o} e^{-wt} \\\\e^{-wt} = \frac{A}{A_{o}}\\\\-wt = \ln \frac{A}{A_{o}}\\\\= -2.079\\\\t = 1.7199 \times 10^{4} \ years\\\\\sim \ 17200\ years\\[/tex]

C₁₀H₁₄N₂ is the empirical formula of the compound whose mass is 40.57 present in 0.2500 moles.

Alkaloid compounds are those naturally present organic compounds in which nitrogen is present.

First we calculate the molecular mass of wanted compound by using the below formula:

n = W/M, where

n = no. of moles = 0.2500 moles (given)

W = given mass = 40.57 grams (given)

M = molar mass = 40.57 grams/= 0.2500 moles = 162.28 g/mole

In the question, given that:

% composition of carbon = 74.02%

% composition of hydrogen = 8.710%

% composition of nitrogen = 17.27%

Now we calculate the mass of these composition by using the below formula:

Composition mass = compound mass * % composition / 100

Mass of carbon = 162.28 * 74.02 / 100 = 120.11g

Mass of hydrogen = 162.28 * 8.710 / 100 = 14.13g

Mass of nitrogen = 162.28 * 17.27 / 100 = 28.02g

Now we calculate the moles of these composition to made empirical formula as:

Moles of carbon = 120.11 / 12 = 10

Moles of hydrogen = 14.13 / 1 = 14

Moles of nitrogen = 28.02 / 14 = 2

Thus, the empirical formula of the compound is C₁₀H₁₄N₂.

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Answer:

A redox reaction in which a change of oxidation number of the reacting species occurs either by oxidation or by reduction which occur simultaneously and to the same extent during the reaction.

Silver atoms are oxidized while oxygen atoms are reduced by a loss of electrons and a gain of electrons respectively.

Explanation:

A redox reaction in which a change of oxidation number of the reacting species occurs either by oxidation or by reduction which occur simultaneously and to the same extent during the reaction.

In a redox reaction,the two reactions occurring simultaneously can be divided into two half reactions; an oxidation half-reaction and a reduction half-reaction.

The oxidation half-reaction involves losing electrons and thus an increase in oxidation number of the species being oxidized. Whereas, the reduction half reaction involves gaining electrons and thus, a reduction innthe oxidation number of the species being reduced.

The species which oxidizes another species is known as an oxidizing agent and isnitself reduced due to its accepting electrons from the species being oxidized. Th reducing agent reduces another species and is itself oxidized as it loses electrons to the oxidized agent.

In the given reaction as shown below:

4 Ag (s) + 2 H₂S (g) + O₂ (g) ---> 2 Ag₂S (s) + 2 H₂0 (g)

The reaction is a redox reaction as a change innthe oxidation number of the reacting species; both oxidation and reduction occurs simultaneously and to the same extent.

The metallic silver atoms, have an oxidation number of zero initially. However, each of the four moles of atoms give up one mole of a electrons each to become oxidized to silver (i) ions, Ag+.

On the other hand, molecular oxygen gas also having oxidation number of zero becomes reduced to oxygen ion, O²-. Each of the two moles of atom in the oxygen gas molecule accept two electrons each donated by the metallic silver atoms to become reduced to oxygen ion, O²-.

The oxidation numbers of hydrogen ion and sulfide ion do not change.

Answer:

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Answer:

One compound, called n-butane, where the prefix n- represents normal, has its four carbon atoms bonded in a continuous chain. The other, called isobutane, has a branched chain. Different compounds that have the same molecular formula are called isomers.

Answer:

d. constitutional isomers​

Explanation:

i hope it will help

Suppose you have a material in it's liquid phase. As you give energy to that liquid, the temperature of the liquid will increase gradually, and the relation between the increase of temperature and the given energy is the specific heat.

Now, there is a point, a critical point, where the temperature stops to increase, which means that we are near a change of phase. So from this point on, the energy is not used to increase the kinetic energy of the particles (which would increase the temperature), the energy is used to break the bonds and allow a change of phase, for example, from liquid to gas.

So, we know that if you have a mol of water at 100°C, then you need to add 40.7 kJ of energy to change the phase of the water from liquid to gas phase.

This means that if you have a mol of water and you give that exact energy, the temperature will not change, instead, you now will have a mol of water at the temperature of 100°C.

Similarly with the case at 25°C (which happens for a particular pressure only)

So the heat of vaporization can not really be related to increases in temperature as you thought.

For changes in temperature, you need to use the specific heat.

We know that for water it is:

c = 4.184 J/g*°C = 76.15 J/mol*°C

So, if you want to increase the temperature from 25° to 100°

This means an increase of 75°C of one mol of water.

We just need to multiply the above number by:

1mol*(75°C)

Energy needed = (76.15 J/mol*°C)*1mol*(75°C) = 5,711.25 J

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Answer: Hello your question is incomplete attached below is the missing image

answer:

Reduction half-reaction: Zn(s) ⇒ Zn⁺² (aq)  + 2e⁻ ( occurs at anode )

Oxidation half-reaction; CO²⁺(aq) + 2e⁻ ⇒ CO (s)  ( occurs at the cathode )

Overall cell reaction ; Zn(s)  + CO²⁺(aq)  ⇒ Zn⁺² (aq) +  CO (s)

Explanation:

stating the standard reduction potentials

E° zn²⁺/zn = -0.76 v

E°Co²⁺ / Co = -0.28 v

since ; -0.76 v  < -0.28 v.    Zn will be oxidized while Co²⁺ will be reduced .

Reduction half-reaction: Zn(s) ⇒ Zn⁺² (aq)  + 2e⁻ ( occurs at anode )

Oxidation half-reaction;  CO²⁺(aq) + 2e⁻ ⇒ CO (s)  ( occurs at the cathode )

hence the

Overall cell reaction ;

Zn(s)  + CO²⁺(aq)  ⇒ Zn⁺² (aq) +  CO (s)

Answer:

Biphenyl

Explanation:

The reaction of bromo benzene with magnesium-ether solution yields a Grignard reagent.

The byproduct of this reaction is biphenyl. It is formed when two unreacted bromobenzene molecules are coupled together.

Hence, It is advised that the bromobenzene solution be added slowly to the magnesium-ether solution so that it isn't present in a high concentration, thus reducing the amount of biphenyl by-product formed.

Answer:

The order is:

F >Be >Li >Ba

Explanation:

Electrons are held in atoms by their  attraction to the nucleus which means that to remove an electron from the atom energy is needed.

The ionization energy is the minimum energy necessary to remove an electron from an atom in the gas phase and ground state, the electron removed being the outermost, that is, the furthest from the nucleus. The further away the electron is from the nucleus, the easier it is to remove it, that is, the less energy is needed.

By increasing the atomic number of the elements of the same group, the nuclear attraction on the outermost electron decreases, since the atomic radius increases. Then the ionization energy decreases. In other words, in a group it decreases from top to bottom because the size of the atom increases and it is easier to remove an external electron.

By increasing the atomic number of the elements of the same period, the nuclear attraction on the outermost electron increases, since the atomic radius decreases. Therefore, in a period, as the atomic number increases, the ionization energy increases. In summary, in a period it increases from left to right as the effective nuclear charge increases and it increases thanks to the decrease in the size of the atom.

Taking these considerations into account, the order is:

F >Be >Li >Ba

Answer

The properties of fatty acids and of lipids derived from them are markedly dependent on chain length and degree of saturation. Unsaturated fatty acids have lower melting points than saturated fatty acids of the same length. For example, the melting point of stearic acid is 69.6°C, whereas that of oleic acid (which contains one cis double bond) is 13.4°C. The melting points of polyunsaturated fatty acids of the C18 series are even lower. Chain length also affects the melting point, as illustrated by the fact that the melting temperature of palmitic acid (C16) is 6.5 degrees lower than that of stearic acid (C18). Thus, short chain length and unsaturation enhance the fluidity of fatty acids and of their derivatives.

Answer:

Explanations you mom bumb it’s a:

It’s 2

Answer:

2.21% wt/v

Explanation:

The mass/volume percentage, %wt/v, is an unit of concentration used in chemistry defined as 100 times the ratio of the mass of solute in g (In this case, CaCl2 = 1.77g) and the volume of solution in mL = 80mL

The %wt/v of this solution is:

%wt /v = 1.77g / 80mL * 100

%wt/v = 2.21% wt/v

Answer:

x= 300m , 38s

answer is 7.9

Answer:

speed=distance/time

Explanation:

speed=300/38

=7.8947368421

to the nearest tenth=7.9

Answer:

A fire class is a system of categorising fire with regard to the type of material and fuel for combustion. Class letters are often assigned to the different types of fire, but these differ between territories. There are separate standards for the United States, Europe, and Australia

Answer:

See explanation

Explanation:

A redox reaction equation shows a gain/loss of electrons from left to right in a reaction. In a redox reaction, a specie looses electrons while another specie gains electrons.

Considering the equation; 2Al(s) + 3Cu(NO3)2(aq) -----> 3Cu(s) + 2Al(NO3)3(aq)

The oxidation state of Al reactant is zero since the oxidation state of all uncombined elements is zero. The oxidation state of All in the product is +3

The oxidation state of the copper in the reactant is +2. The oxidation state of copper in the product is zero.

The oxidation state of N in the reactant and product is +5.

The oxidation state of oxygen in the reactant and product is (-2).

This is a redox reaction because from left to right, Al was oxidized (oxidation number increased from zero to +3) while Cu was reduced (oxidation number decreased from +2 to zero).

Answer:

89°c

Explanation:

i think this is the answer cause the temperature changed from 11 to 100 and so the atmospheric temperature would be the change in temperature

100-11=89°c

I hope this helps and sorry if it's wrong

Explanation:

Amount of water required in each case:

(a)The mass% of the solution is:9.95

Mass of solute that is urea is 6.80 g

To determine the mass of solvent water use the formula:

[tex]mass percent=\frac{mass of solute}{mass of solution} x 100\\\\9.95=(6.80g/mass of solution )x100\\mass of solution =(6.80 /9.95)x100\\=68.3 g[/tex]

Hence the mass of solvent = mass of solution - the mass of solute

=68.3 g - 6.80g

=61.5 g

Hence, the answer is mass of solvent water required is 61.5 g.

(b) Given mass%=1.70

mass of solute MgBr2 = 29.3 g

The mass of solvent water required can be calculated as shown below:

[tex]mass percent=\frac{mass of solute}{mass of solution} x 100\\\\1.70=(29.3g/mass of solution )x100\\mass of solution =(29.3 g /1.70)x100\\=1720 g[/tex]

The mass of the solution is 1720 g.

Mass of solvent water = mass of solution - mass of solute

=1720 g - 29.3 g

=1690.7 g

Answer: The mass of water required is 1690.7 g.

Answer:

The correct answer is "654.54 nm".

Explanation:

According to the question,

⇒ [tex]\frac{1}{\lambda}= Rh(\frac{1}{n1^2} -\frac{1}{n2^2} )[/tex]

By substituting the values, we get

       [tex]=1.1\times 10^7(\frac{1}{4} -\frac{1}{9} )[/tex]

       [tex]=1.1\times 10^7(\frac{9-4}{36} )[/tex]

       [tex]=1.1\times 10^7(\frac{5}{36} )[/tex]

       [tex]=654.54\ nm[/tex]

Thus the above is the right solution.

The correct order of the substances in order of decreasing boiling point is,

KF , CH30OH , CO2 , Ne

Boiling point, the temperature at which the force exerted by the surroundings upon a liquid exists equaled by the pressure exerted by the vapor of the liquid; under this situation, the addition of heat affects the transformation of the liquid into its vapor without increasing the temperature.

The main difference between the boiling point and the melting point stands that the melting point is determined as the temperature at which solid and liquid phases exist in equilibrium, whereas the boiling point stands as the temperature at which the vapor pressure of a liquid stands equal to the external pressure.

Hence, The correct order of the substances in order of decreasing boiling point is,

KF , CH30OH , CO2 , Ne

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Answer:

Average specific heat capacity of metal = 0.57 J/g°C

Explanation:

Heat lost = Heat gained

Heat energy gained or lost, H = mcΔT

where m = mass of substance, c = specific heat capacity, ΔT = temperature change

Trial 1:

Heat lost by metal = -[2.746 g × c × ΔT]

ΔT = (26.3 - 72.1) °C = -45.8 °C

Heat lost by metal = -[2.746 g × c × (-45.8 °C)] = c × (125.7688)g°C

Heat gained by water = 15.200 × 4.18 × ΔT

ΔT = (26.3 - 24.7) = 1.6 °C

Heat gained by water = 15.200 × 4.18 × 1.6 = 101.6576 J

From Heat lost = Heat gained

c × (125.7688)g°C = 101.6576 J

c = 101.6576 J / 125.7688 g°C

c = 0.8083 J/g°C

Trial 2:

Heat lost by metal = -[2.750 g × c × ΔT]

ΔT = (26.2 - 72.2)°C] = - 46 °C

Heat lost by metal = -[2.750 g × c × (-46 °C)

Heat lost by metal = c × (126.5) g°C

Heat gained by water = 15.206 × 4.18 × ΔT

ΔT = (26.2 - 24.6) = 1.6 °C

Heat gained by water = 15.206 × 4.18 × 1.6 = 101.697728 J

From Heat lost = Heat gained

c × (126.5)g°C = 101.6977 J

c = 101.697728 J / 126.5 g°C

c = 0.8039 J/g°C

Trial 3:

Heat lost by metal = -[2.900 g × c × ΔT]

ΔT = (24.7 - 71.9)°C] = - 47.2 °C

Heat lost by metal = -[2.900 g × c × (- 47.2 °C)

Heat lost by metal = -[2.900 g × c × (- 47.2)°C] = c × (136.88)g°C

Heat gained by water = 15.201 × 4.18 × ΔT

ΔT = (24.7 - 24.5) = 0.2 °C

Heat gained by water = 15.201 × 4.18 × 0.2 = 12.708036 J

From Heat lost = Heat gained

c × (136.88)g°C = 12.708036 J

c = 12.708036 J / 136.88 g°C

c = 0.0928 J/g°C

Average specific heat capacity of metal = (0.8083 + 0.8039 + 0.0928) J/g°C / 3

Average specific heat capacity of metal = 0.57 J/g°C

Lester Brown thinks reducing carbon dioxide emissions 80% by 2050 is not fast enough.

Lester Brown is an American environmentalist who has focused on studying the environment and its protection. In recent years, he has made alerts for world leaders and large industries to strive to stop CO2 emissions because this greenhouse gas has a massive influence on global warming.

Therefore, Lester Brown considers that the projections of reduction of greenhouse gases (especially CO2) made by the world powers for the year 2050, ignore the reality because he considers that CO2 emissions must decrease by at least one 80% in 2020 to avoid drastic consequences in current living conditions. Therefore, the answer is B.

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Answer:

Tapeworms and roundworms both belong to the same phylum however, their families are different from one another.

Tapeworms are flat, segmented intestinal parasites of the cat and dog and humans sometimes. They are present in the intestines of pets and depend on them, therefore, are parasites. These parasites look like tape which gives it its name.

Roundworms can also infect humans and the most common cases are among children. When not treated immediately, they can cause severe damage to a human host and can even cause blindness. Tapeworms are white in color with a long, segmented body.

Answer:

[tex]\rho_t=1025000 gmL^{-1}[/tex]

Explanation:

From the question we are told that:

Density of acetic acid [tex]\rho_a=205 gL^{-1}[/tex]

Density of Water [tex]\rho_w=820 gL^{-1}[/tex]

Generally the equation for Solution Density is mathematically given by

[tex]\rho_t= \rho_w+\rho_a[/tex]

[tex]\rho_t=205+820[/tex]

[tex]\rho_t=1025 gL^{-1}[/tex]

[tex]\rho_t=1025000 gmL^{-1}[/tex]

Answer:

Molarity is a measure of concentration

I Hope its right if not so advance sorry :)

The molarity measures the number of moles of the solute present per liter of the solution and it measures the concentration of the solution. option D is correct.

Molarity is the amount or the number of moles present in per liter of the solution it is the unit to measure the concentration of the moles.

Unit of molarity will be moles per liter and the temperature does not affect the molarity of the solution. molarity can be calculated by dividing the concentration of the solution by the molar mass of the given element.

molarity = weight / mass ×  1000/ volume in liters.

With the help of this formula, we can calculate the molarity.

Therefore,  molarity measures the number of moles of the solute present per liter of the solution and it measures the concentration of the solution. option D is correct.

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Answer:

Vien, sometimes we make problems like this harder than they need to be. Suppose I asked you, “How many dozen wheels are on four dozen automobiles?” You would have no trouble answering 4 x 4 = 16 dozen.

A mole is just a quantity like a dozen. And in this case, instead of 4 wheels, each C2F6 molecule bears 6 fluorine atoms, right?

So 4 x 6 = 24 moles of fluorine atoms. You’ve got this, Vien!

Answer:

There is no difference between the two.

Explanation:

They both show the same volume. But, adding decimal places shows the least count of the instrument used and is more acceptable when recording values in scientific experiments

Answer:

"[tex]N^+(g) \rightarrow N^{2+}(g) + e^-[/tex]" is the appropriate answer.

Explanation:

Thus the above is the correct answer.