which of the following substance is an element?
A. Air
B. Iron
C. Salt
D. Sugar​

Answer:

batteries

Explanation:

bc they're powered by energy

Answer:

Compact fluorescent lamps, or CFLs, use 75 percent less energy than a traditional incandescent bulb, but they never quite caught on for home use.Feb

There are various kind of elements that are present in periodic table. Elements that are metals are kept on left side of periodic table and elements which are non metals are kept on right side of periodic table.

Periodic table is a table in which we find elements with properties like metals, non metals and metalloids element arranges in increasing atomic number.

The first 20 elements of periodic table are Hydrogen, Helium, Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, Neon, Sodium, Magnesium, Aluminum, Silicon, Phosphorus, Sulfur, Chlorine, Argon, Potassium and Calcium. Out of these Lithium, Beryllium, Sodium, Magnesium. Potassium and Calcium are metals so they are kept on the left side of the periodic table while others are non metals so they are kept on right side of periodic table.

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Answer:

• the warmth from the sun

• the heat from another a heater

• A cup of hot chocolate

•baking in an oven

Two everyday example that we say for the thermal energy of a substance being increased are, faster movement of the substances and boiling if liquids as well light absorption.

Thermal energy is a form of energy generated by heating up a substance. It can also be generated by the movement of its particles.

Vibrating molecules increases the thermal energy of a substance. Similarly, when we heat a substance it acquires more thermal energy.

Another way of increasing thermal energy is light absorption by the substance. Thermal energy associated with light increases the temperature of of the system which is absorbed the light.

Hence, the two ways by which thermal energy of a substance is increased are heating or boiling and faster movement.

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Answer:

Ksp = 8.99x10⁻¹²

Explanation:

The solubility of Mg(OH)₂ is described with the reaction:

Mg(OH)₂(s) → Mg²⁺(aq) + 2OH⁻(aq)

The solubility product, Ksp, is:

Ksp = [Mg²⁺] [OH⁻]²

As you can see from the reaction, when 1 mole of Mg²⁺ is produced, 2 moles of OH⁻ are produced too, if [Mg²⁺] is 1.31x10⁻⁴M, [OH⁻] = 2.62x10⁻⁴M

Replacing:

Ksp = [Mg²⁺] [OH⁻]²

Ksp = [1.31x10⁻⁴M] [2.62x10⁻⁴M]²

The solubility product of the [tex]\rm Mg(OH)_2[/tex] has been [tex]\rm 8.99\;\times\;10^{-12}[/tex].

The balanced equation for the dissociation of Magnesium hydroxide has been:

[tex]\rm Mg(OH)_2\;\rightarrow\;Mg^2^+\;+\;2\;OH^-[/tex]

From the balanced chemical equation, dissociation of 1 mole magnesium hydroxide has been resulted in the 1 mole magnesium and 2 mole hydroxide ions.

Since, given magnesium concentration, [tex]\rm Mg^2^+=1.31\;\times\;10^-^4\;M[/tex]

The concentration of hydroxide ion, [tex]\rm OH^-[/tex] will be:

[tex]\rm 1\;M\;Mg^2^+=2\;M\;OH^-\\1.31\;\times\;10^-^4\;M=1.31\;\times\;10^-^4\;\times\;2\;M\;OH^-\\1.31\;\times\;10^-^4\;M=2.62\;\times\;2\;M\;OH^-\\[/tex]

The solubility product (ksp) of the reaction has been given as:

[tex]ksp=\rm [Mg^2^+]\;[OH^-]^2[/tex]

Substituting the values for ksp:

[tex]ksp\;=\rm [1.31\;\times\;10^-^4]\;[2.62\;\times\;10^-^4]^2\\\textit ksp=8.99\;\times\;10^-^1^2[/tex]

The solubility product of the reaction has been [tex]\rm 8.99\;\times\;10^{-12}[/tex].

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Answer:

An increase in the concentration of the reactant in solution causes the reaction rate to increase exponentially - first order

The reaction rate increases in direct proportion to the concentration of the reactant in solution -second order

The reaction rate is constant regardless of the amount of reactant in solution - zero order

Explanation:

The Order of Reaction refers to the power dependence of the rate on the concentration of each reactant. The order of reaction is determined experimentally and not necessarily by inspection.

Typically, in a second order reaction, the rate of reaction increases in proportion to increase in concentration.

For a first order reaction, the rate of reaction increases exponentially as the increase in concentration.

For a zero order reaction, the rate of reaction is independent of the concentration of the reactant.

Answer:

Um, I'd say add more types of plants cause different plants react differently to things, I guess?

Answer:

On a warm day, water absorbs from its warmer environment, lowering the air tempurature. On a cool night, heat is transferred from the water to its cooler environment, raising the air tempura

Explanation:

Answer:

Mitochondria is the powerhouse of the cell, but don't let this distract you from the fact that Mr. Krabs sold SpongeBob's soul for 62 cents

Answer:

mitochondria

Explanation:

Answer:

Zinc weighs 65.38 grams per mole, so we’ve got 0.994 moles of zinc (I’ll worry about sig figs at the end). HCl weighs 36.46 grams per mile, so we’ve got 1.78 moles of HCl. However, two moles of HCl react with one mole of zinc. So only 1.78/2 = 0.890 moles of Zinc are going to react.

One mole of zinc produces one mole of hydrogen, which weigh 2.02 grams per mole. So 0.890 moles * 2.02 grams/mole means 1.90 grams of hydrogen will be produced.

Since we have 2 sig figs in the weights given, the answer should have 2 sig figs, thus 1.9 grams.

This is just an example

Answer:

the reactivity and the valence electrons

Explanation:

the reactivity of the elements would have played a significant role in why such elements were grouped together. the number of valence electrons dictates how reactive an element is - the less valence electrons the more reactive it is. the column, group 1 in which these elements are put together in, show that each of the elements have 1 valence electrons and are therefore reactive.

you can go on to further explain what valence electrons are, explain what the group numbers are associated with the valence electrons and how valence electrons effect reactivity. further this, talk about how the three elements have the same number of valence electrons and therefore were grouped together

Answer:

i think the answer is true pls mark branliest

Explanation:

Answer:

its true! earth quakes do form huge gaps in the earth surface

Explanation:

Answer:

The amount of salt solution.

Explanation:

so first you have to think about it as a y = mx + b function, where m and x are constants. So basically the independent variable is represented by the amount of salt solution because the health of the patient is affected by the amount of salt solution. this is how you would write it out as an equation so you can understand it better.

The Health of the patient   = The amount of salt solution + b

Since y depends on the values of m, x, and b, The amount of salt solution would be the independent variable.

Answer : The correct option is A: 20 km/h, B: 10 km/h

Explanation :

Speed : It is defined as the distance traveled per unit time.

Formula used:

[tex]S=\frac{d}{t}[/tex]

where,

S = speed

d = distance

t = time

First we have to calculate the speed of vehicle A.

Given:

Distance of vehicle A = 50 km

Time of vehicle A = 2.5 hr

Now putting all the given values in the above formula, we get:

[tex]S=\frac{50km}{2.5hr}=20km/hr[/tex]

Now we have to calculate the speed of vehicle B.

Given:

Distance of vehicle B = 50 km

Time of vehicle B = 5 hr

Now putting all the given values in the above formula, we get:

[tex]S=\frac{50km}{5hr}=10km/hr[/tex]

Therefore, the speed of vehicle A and B is 20 km/hr and 10 km/hr respectively.

Answer:

0.84 g/cm3 EDGE 2020

Explanation:

Answer:

What is the density of the football while it is deflated?

⇒ 0.84 g/cm3

Answer:

Magnesium loses it's two electrons and Oxygen gains two electrons. Magnesium is now a cation and Oxygen is now an anion. Both become stable.

Explanation:

The type of electron transfer which happens between the Mg and O atom is a complete transfer of electrons from the Mg atom to the O atom in an ionic bond.

The most electropositive electron usually is usually the donor while the most electronegative elements is the acceptor.

As evident in the case above;

Ultimately, an ionic bond is formed between the Mg and O atoms.

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Answer:

The answer is heterogeneous mixture

Answer:

YESBSJSKSSKEKEJRJRJER

Answer:

The correct answer is - option B. 4.

Explanation:

The visible spectrum of light emitted by a sample of active or excited hydrogen atoms splits into four wavelengths that are basically four distinct levels of energy in the visible region of the spectrum. There four different wavelengths are 410 nm, 434 nm, 486 nm, and 656 nm.

These shows for colors according to the spectrum and wavelength violet, blue, green, and red, where 656 nm wavelength is most intense on the spectrum.

If a hydrogen atom emits red, blue-green, blue, and violet light, the number of energy levels it has in the visible region of the spectrum is: B. 4

An electromagnetic spectrum can be defined as a range of frequency and wavelength that an electromagnetic wave is distributed (extends).

Generally, the electromagnetic spectrum comprises the following:

When the atom of an element emits a radiation, each color of the radiation represents an energy level within the visible region of the electromagnetic spectrum.

Since the hydrogen atom emitted four colors (red, blue-green, blue, and violet light), it has four (4) energy levels in the visible region of the electromagnetic spectrum.

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Answer:

Quantum Mechanical

Explanation:

This current atomic model evolved from the earlier Rutherford-Bohr model, which compared electrons orbiting an atomic nucleus to planets orbiting the sun. The newest understanding of atomic makeup in the Electron Cloud Model better represents observed atomic phoneme since the Bohr model rose to prominence.

Answer:

Electron cloud model

Explanation:

Complete question

The complete question is shown on the first uploaded image

Answer:

The value is  [tex]K_c  =  2.69 *10^{-5} [/tex]  

Explanation:

From the question we are told that

   The equation is  

           [tex]Fe_20_3_{(s)}+3H_{(g)}\to2Fe_{(s)}+3H_2O_{(g)}[/tex]

Generally the equilibrium is mathematically represented as

        [tex]K_c  =  \frac{[H_2O]^2}{[H_2]^3}[/tex]

Here [tex][H_2O][/tex] is the concentration of water vapor which is mathematically represented as

      [tex][H_2O ] =  \frac{n_w}{V_s }[/tex]

Here [tex]V_s[/tex] is the volume of the solution given as 8.9 L

[tex]n_w[/tex] is the number of moles of water vapor which is mathematically represented as

        [tex]n_w  =  \frac{m_w}{Z_w}[/tex]

Here  [tex]m_w[/tex]  is the mass of water given as 2.00 g

and   [tex]Z_w[/tex]  is the molar mass of water with value  18 g/mol

So  

         [tex]n_w  =  \frac{2}{18}[/tex]

=>     [tex]n_w  = 0.11 \  mol[/tex]

So

     [tex][H_2O ] =  \frac{0.11}{8.9 }[/tex]

=>   [tex][H_2O ] = 0.01236 \  M [/tex]

Also

[tex][H][/tex] is the concentration of hydrogen gas which is mathematically represented as

      [tex][H ] =  \frac{n_v}{V_s }[/tex]

Here [tex]V_s[/tex] is the volume of the solution given as 8.9 L

[tex]n_v[/tex] is the number of moles of  hydrogen gas which is mathematically represented as

        [tex]n_v  =  \frac{m_v}{Z_v}[/tex]

Here  [tex]m_w[/tex]  is the mass of water given as 4.77 g

and   [tex]Z_v[/tex]  is the molar mass of water with value  2 g/mol

So  

         [tex]n_w  =  \frac{4.77}{2}[/tex]

=>     [tex]n_w  = 2.385 \  mol[/tex]

So

     [tex][H_2O ] =  \frac{2.385}{8.9 }[/tex]

=>   [tex][H_2O ] =  0.265 \  M [/tex]

So

     [tex]K_c  =  \frac{( 0.01236 )^3}{ (0.265 )^2}[/tex]

=>   [tex]K_c  =  2.69 *10^{-5} [/tex]  

Answer:

[tex]Kc=3.8x10^{-7}[/tex]

Explanation:

Hello.

In this case, for the chemical reaction:

[tex]2CH_3OH(l)+3O_2(g)\rightarrow 2CO_2(g)+4H_2O(g)[/tex]

We write the equilibrium expression including the gaseous or aqueous species only, that is why the methanol is not included due to heterogeneous equilibrium:

[tex]Kc=\frac{[CO_2]^2[H_2O]^4}{[O_2]^3}[/tex]

Whereas each gaseous species is powered to its stoichiometric coefficient (number before the species). In such a way, considering the equilibrium masses of carbon dioxide (44 g/mol), water (18 g/mol) and oxygen (32 g/mol) to be 1.56 g, 2.28 g and 3.33 g respectively, we compute the moles as we need molar concentrations in the equilibrium constant calculation:

[tex]n_{CO_2}=1.56g/(44g/mol)=0.0355mol\\\\n_{H_2O}=2.28g/(18g/mol)=0.127mol\\\\n_{O_2}=3.33 g/(32g/mol)=0.104mol[/tex]

Thus, into the 9.3.L vessel, the equilibrium concentrations are:

[tex][CO_2]=\frac{0.0355mol}{9.3L}=0.00382M[/tex]

[tex][H_2O]=\frac{0.127mol}{9.3L}=0.0137M[/tex]

[tex][O_2]=\frac{0.104mol}{9.3L}=0.0112M[/tex]

Therefore, the equilibrium constant shown with two significant figures is:

[tex]Kc=\frac{(0.00382M)^2(0.0138M)^4}{(0.0112M)^3} \\\\Kc=3.8x10^{-7}[/tex]

Best regards.

Answer:

(a) [tex]\Delta H=-73.1\frac{kJ}{mol}[/tex]

(b) [tex]T_2=38.1\°C[/tex]

(c) Yes, it is appropriated.

Explanation:

Hello.

(a) In this case, given the formation enthalpies for copper (II) sulfate, copper (II) ion and sulfate ion, we can compute the enthalpy change for such process as follows:

[tex]\Delta H=\Delta H_{Cu^{2+}}+\Delta H_{SO_4^{-2}}-\Delta H_{CuSO_4}\\\\\Delta H=64.8-909.3-(-771.4)\\\\\Delta H=-73.1\frac{kJ}{mol}[/tex]

(b) In this case, since 13.0 g of copper (II) sulfate (molar mass: 159.55 g/mol) we can compute the gained heat by water via:

[tex]Q_{water}=-n_{CuSO_4}\Delta H=-13.0g*\frac{1mol}{159.55g}* -73.1\frac{kJ}{mol}\\ \\Q_{water}=5.96kJ=5960J[/tex]

As the heat lost by the reaction is gained by the water, therefore, the final temperature is:

[tex]Q_{water}=m_{water}Cp_{water}(T_2-T_1)\\\\T_2=T_1+\frac{Q_{water}}{m_{water}Cp_{water}}\\ \\T_2=25.0\°C+\frac{5960J}{0.109L*\frac{1000g}{1L}*4.18\frac{J}{g\°C} } \\\\T_2=38.1\°C[/tex]

(c) In this case, since this dissolution reaction is exothermic as it increases the temperature when undergone, we can infer that yes, this dissolution would be appropriate for the preparation of a hot pack, because a cold pack would be with an endothermic dissolution reaction.

Best regards.

Answer:

Metalloids are brittle like Non-Metals

Explanation:

Answer:

Control group

Answer:

268.3 m/sec

Explanation:

Answer: conclusion

Explanation:

It say reviews your original question and your hypothesis

Answer:

conclusion!

Explanation:

Answer:

, containing 2.65 X 1020 molecules.

Explanation:

The mass of a sample of fruit sugar (fructose) C₆H₁₂O₆, containing 2.65 ×10²⁰ is equal to 2.88 g.

Avogadro’s number can be defined as the number of units in one mole of any chemical substance. Generally, these entities can be electrons, molecules, atoms, ions, or protons, depending upon the kind of chemical reaction or reactants and products.

The value of Avogadro’s constant is found approximately 6.022 × 10²³ mol⁻¹.

Given, the number of molecules of fructose = 2.65 ×10²⁰

The molar mass of the fructose = 180.16 g/mol

So 6.022 × 10²³ molecules of fructose have mass = 180.16 g

Then 2.65 × 10²⁰ fructose molecules will have mass = 2875.04 × 10⁻³ g

The mass of the  2.65 × 10²⁰ fructose molecules =  2.88 g

Therefore, the mass of  2.65 × 10²⁰ fructose molecules is equal to 2.88 g.

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