which of these is an element?

KBr
O2
2KCl
FeO2

Answers

Answer 1

Answer:

02

Explanation:

all the other options given are compounds


Related Questions

Select the correct answer.
In which situation is no work considered to be done by a force?

A.
when the angle between the force and displacement is 180°
B.
when the angle between the force and displacement is 90°
C.
when the angle between the force and displacement is 45°
D.
when the angle between the force and displacement is 0°

Answers

Answer:

Explanation:

when the angle between the force and  displacement is 0

1. Compare and contrast the characteristics of metals and nonmetals.
2. Describe the electrochemical series and why it’s important in understanding metals.
3. Describe the theory of ionization in regard to acids and bases.
4. Identify the role of indicators.

Answers

Answer:

1. Both metals and nonmetals are types of elements and can be involved in chemical reactions. Some of their differences are highlighted in the chart below.

  Metals:    

Appearance; Shiny.    

Conduct heat or electricity; Yes.  

Malleable or ductile; Yes, both and has great mechanical strength.    

Form stable compounds; Forms stable compounds with acids; also forms oxides; replaces hydrogen in acids or water; combine with nonmetals; often becomes positive.

  Nonmetals :  

Appearance; Not shiny .  

Conduct heat or electricity; Not well .  

Malleable or ductile; Brittle and not easily molded into shapes .  

Form stable compounds; Oxides usually give acid reactions in water; often becomes negative

2. The electrochemical series is an arrangement of metals in such order that any metal in the list is displaced from its compounds by any metal above it, but displaces any metal below it. The higher up the list a metal is, the greater its activity. Knowing a metal’s placement on this chart can help you understand the activity of the metal, especially in regard to its ability to displace hydrogen in acids. Any items on the list far above hydrogen will do a good job at displacing it, those near it won’t do such a good job, and those below it won’t displace it from acids at all.

3. When placed in water, acids dissociate and form free hydrogen ions, which determine the properties of acids. The number of hydrogen ions determines the strength of an acid. Strong acids dissociate to a large degree and produce a large number of hydrogen ions. Weak acids dissociate to only a slight degree.

When placed in water, bases dissociate and form free hydroxyl ions, which determine the properties of bases. Strong bases dissociate to a great degree and produce a large number of hydroxyl ions. Weak bases dissociate to only a slight degree.

When free hydrogen ions and free hydroxyl ions are removed from solutions of acids and bases, then the acidic and basic properties disappear. This is what happens when acids and bases are mixed together in proper proportion; the hydroxyl ion will unite with the hydrogen ion to form water. The resulting salt product is neutral.

4. Indicators are used to help determine the pH value of an unknown solution. These are often papers that turn a certain color at certain pH values.

Metals are good conductors of heat and electricity but the non-metals are not.

Compare metals and non-metals

Metals are good conductors of electricity and heat whereas non-metals are poor conductors of heat and electricity. Metals have high density while on the other hand, non-metals have low density. Metals are malleable and ductile whereas non-metals are brittle.

So we can conclude that metals are good conductors of heat and electricity but the non-metals are not.

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Does changing the number of protons change the identity of the element you have built ?

Answers

Answer: Yes.

Explanation:

the number of protons in the nucleus determines an element's identity. Chemical changes do not affect the nucleus, so chemical changes cannot change one type of atom into another. The number of protons in a nucleus does change sometimes, however. The identity of the atom, therefore, changes.

Which ecosystem is the least stable?

Answers

Answer:

tundra bc it has barley any food source and has vary little inhabitants

Explanation:

Answer:

a patch of lichens on bare rock

I’ll give the Brainliest, you also need to explain how the answer you got is correct.

Choose the best description of a neap tide.

A. Neap tides produce during the highest tides of the month.

B. Neap tides happen during winter and summer.

C. Neap tides could be described as low high tides and high low tides.

D. A neap tide is the period halfway between tides when the tide changes direction.

Thank you!

Answers

Answer:

D. A neap tide is the period halfway between tides when the tide changes direction. (correction) Answer : C

Explanation:

Process of elimination can be used. First off, A is incorrect because neap tides have the smallest tidal range ; spring tides would fit this choice. B is incorrect since neap tides are specific to the first, and third quarter moons when the sun and moon are right angles. C is wrong because it is the other way around since high tides are a little higher than average and low tides are a little lower than average (correction) this is correct since higher low tides and lower high tides are closer together and have a smaller tidal range than standard tides(spring tides) with higher high tides, and lower low tides. D is correct because they occur halfway between the spring tides (correction): incorrect since a neap tides occur around a week(7 days) after a spring tide(moderate tides). There is no evidence this is true.

There are three patterns: diurnal(one high and low tides a day), semidiurnal(two high and low tides a day), and mixed(two high and low tides a day of different lengths).

The spring and neap tides are the types of tides involved with the low and high tides.

PLZ ANSWER WILL GIVE BRAINLIEST ASAP
Given the data below, what substance does not show a reaction for any of the tests? Hint: (+)= reaction occurred, (-)= no reaction

unknown
salt
Corn starch
Gelatin

Answers

Answer:

Salt

Explanation:

It has all -

Write a balanced equation for the complete oxidation reaction that occurs when ethane burns in air

Answers

Balanced equation : 2C₂H₆ (g) + 7O₂ (g) ⟶ 4CO₂ (g) + 6H₂O (ℓ)Further explanation

Alkanes are saturated hydrocarbons that have single bonds in chains

General formula for alkanes :

[tex]\tt \large{\bold{C_nH_{2n+2}}[/tex]

Hydrocarbon combustion reactions (specifically alkanes)

[tex]\large {\box {\bold{C_nH _ (_2_n _ + _ 2_) + \dfrac {3n + 1} {2} O_2 \Rightarrow nCO_2 + (n + 1) H_2O}}}[/tex]

So that the burning of ethane with air (oxygen):

[tex]\tt C_2H_6+\dfrac{7}{2}O_2\rightarrow 2CO_2+3H_2O[/tex]

2C₂H₆ (g) + 7O₂ (g) ⟶ 4CO₂ (g) + 6H₂O (ℓ)

or we can use mathematical equations to solve equilibrium chemical equations by giving the coefficients for each compound involved in the reaction

C₂H₆ (g) + aO₂ (g) ⟶ bCO₂ (g) + cH₂O (ℓ)

C : left 2, right b ⇒ b=2

H: left 6, right 2c⇒ 2c=6⇒ c= 3

O : left 2a, right 2b+c⇒ 2a=2b+c⇒2a=2.2+3⇒2a=7⇒a=7/2

which of these elements is most likely to be magnesium the most metallic of all samples?

Answers

Answer:

B

Explanation:

Just did it on usa test prep

The element which is most likely to be magnesium  is the element with the electronic configuration same as magnesium.

What is an element?

It is defined as a substance which cannot be broken down further into any other substance. Each element is made up of its own type of atom. Due to this reason all elements are different from one another.

Elements can be classified as metals and non-metals. Metals are shiny and conduct electricity and are all solids at room temperature except mercury. Non-metals do not conduct electricity and are mostly gases at room temperature except carbon and sulfur.

The number of protons in the nucleus is the defining property of an element and is related to the atomic number.All atoms with same atomic number are atoms of same element.

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Which describes the motion of the car as shown by the graph?
A) travels at a constant speed
B) not moving
C) changing directions
D) speeding up

Answers

D) speeding up I think

A metal block, 2.0cm x 2.5cm x 3.0cm, has a mass of 40.5g. What is the density of the sample? What type of metal is the metal block composed of?

Aluminum - 2.699
Copper - 8.92
Iron - 7.874
Lead - 11.43
Nickel - 8.908
Tin - 7.265
Zinc - 7.14

Answers

Answer:

The block is made up of aluminum.

density = 2.7 g/cm³

Explanation:

Given data:

Dimension of metal block = 2.0 cm×2.5 cm× 3.0 cm

Mass of block = 40.05 g

Density of block = ?

Which metal is this = ?

Solution:

Density:

Density is equal to the mass of substance divided by its volume.

The symbol used for density is called rho. It is represented by ρ. However letter D can also be used to represent the density.

Units:

SI unit of density is Kg/m3.

Other units are given below,

g/cm3, g/mL , kg/L

Formula:

D=m/v

D= density

m=mass

V=volume

Volume of block = 2.0 cm×2.5 cm× 3.0 cm = 15 cm³

d = m/v

d = 40.5 g/ 15 cm³

d = 2.7 g/cm³

The block is made up of aluminum.

A piece of wood that measures 2.7 cm x 5.5 cm x 3.9 cm has a mass of 84 g what is the density of the wood

Answers

The density of the wood : 1.45 g/cm³

Further explanation  

Density is a quantity derived from the mass and volume  

Density is the ratio of mass per unit volume  

With the same mass, the volume of objects that have a high density will be smaller than objects with a smaller type of density  

The unit of density can be expressed in g/cm³ or kg/m³  

Density formula:  

[tex]\large {\boxed {\bold {\rho ~ = ~ \frac {m} {V}}}}[/tex]

ρ = density  

m = mass  

v = volume  

Volume of the wood

[tex]\tt V=2.7\times 5.5\times 3.9=57.915~cm^3[/tex]

density

[tex]\tt \rho=\dfrac{m}{V}\\\\\rho=\dfrac{84~g}{57.915~cm^3}=\boxed{\bold{1.45`g/cm^3}}[/tex]

Sodium + oxygen
What colour is the flame produces

Answers

Answer:

Orange

Explanation:

I used google my b

Answer:

ORANGE

explanation:

Small pieces of sodium burn in air with often little more than an orange glow. Using larger amounts of sodium or burning it in oxygen gives a strong orange flame.

HELPPP PLEASEEE!!! calculate the energy of radiation with a wavelength of 432 nm

Answers

Formula:


f = C/λ


Where,

λ (Lambda) = Wavelength in meters

c = Speed of Light (299,792,458 m/s)

f = Frequency (MHz)

answer= 693964023.148148 MHz

Sugar is added to iced tea and the contents are stirred until all of the sugar dissolves. How would the tea now be classified?

Answers

By concentrating the mixes of substances

Identify the law that explains the following observation:
Nitrogen Dioxide can be formed by reacting 14 grams of
nitrogen with 32 grams of oxygen.

Answers

Answer:

Proust's law of definite proportion

Explanation:

The law of constant proportion states that the components elements of a given chemical compound combine with each other in a fixed mass ratio when the compound is produced by any given process

Therefore, from the question, the chemical formula for Nitrogen Dioxide is NO₂, where the molar mass of nitrogen, N = 14

The molar mass of oxygen, O = 16

Given that one molecule of NO₂, contains one atom of nitrogen and two atoms of oxygen, one mole of NO₂ will contain 14 grams of nitrogen and 32 grams of oxygen, according to Proust's law of definite proportion.

(b) Define, in terms of oxidation state, the Oxidizing agent
a substance which gains oxygen
a substance whis lose hydrogen
a substance which experiences a decrease in oxidation state
a substance which experiences an increase in oxidation state​

Answers

Answer: a substance whis lose hydrogen

Explanation:

What is involved in weathering?

Answers

Answer:

the answer is water.Hope this helps

Can you explain what vsepr stand for in your own word?

Answers

Answer:

VSEPR stands for: valence-shell electron-pair repulsion. Which is the study of the molecular geometry. Basically, it accounts for the geometry arrangements of electron pairs around the central atom in terms of the electrostatic repulsion between electron pairs.

Calculate the density of an object with mass = 30.50 g and a volume = 2.20 cm^3​

Answers

Answer:

The answer is 13.86 g/cm³

Explanation:

The density of a substance can be found by using the formula

[tex]density = \frac{mass}{volume} \\ [/tex]

From the question

mass = 30.5 g

volume = 2.2 cm³

We have

[tex]density = \frac{30.5}{2.2} \\ = 13.863...[/tex]

We have the final answer as

13.86 g/cm³

Hope this helps you

What is the volume, in liters, of 1.40 mol of oxygen gas at 20.0°C and 0.974 atm?

Answers

Answer:

V = 34.55 L

Explanation:

Given that,

No of moles, n = 1.4

Temperature, T = 20°C = 20 + 273 = 293 K

Pressure, P = 0.974 atm

We need to find the volume of the gas. It can be calculated using Ideal gas equation which is :

PV=nRT

R is gas constant, [tex]R=0.08206\ L-atm/mol-K[/tex]

Finding for V,

[tex]V=\dfrac{nRT}{P}\\\\V=\dfrac{1.4\times 0.08206\times 293}{0.974 }\\\\V=34.55\ L[/tex]

So, the volume of the gas is 34.55 L.

• True False estion 2 (1 point) Water and ice are made from the same molecule H2O True False ​

Answers

Answer:

true i think

Explanation:

Yeah it’s true just frozen

The millions of fossils that scientists have collected are called the fossil __.

Answers

Answer:

record

Explanation:

Draw a structural formula for the alkene you would use to prepare the alcohol shown by hydroboration/oxidation.

Answers

Answer:

See explanation

Explanation:

The question is incomplete because the image of the alcohol is missing. However, I will try give you a general picture of the reaction known as hydroboration of alkenes.

This reaction occurs in two steps. In the first step, -BH2 and H add to the same face of the double bond (syn addition).

In the second step, alkaline hydrogen peroxide is added and the alcohol is formed.

Note that the BH2 and H adds to the two atoms of the double bond. The final product of the reaction appears as if water was added to the original alkene following an anti-Markovnikov mechanism.

Steric hindrance is known to play a major role in this reaction as good yield of the anti-Markovnikov like product is obtained with alkenes having one of the carbon atoms of the double bond significantly hindered.

Burning is a type of_________reaction.

O replacement
O decomposition
O synthesis
O combustion

Answers

Answer:

Combustion

Explanation:

Happy Halloween!

A foam square has a mass of 25 g and a volume of 90 mL. What is the density?

Answers

Answer:

The answer is 0.28 g/mL

Explanation:

The density of a substance can be found by using the formula

[tex]density = \frac{mass}{volume} \\ [/tex]

So we have

[tex]density = \frac{25}{90} = \frac{5}{18} \\ = 0.277777...[/tex]

We have the final answer as

0.28 g/mL

Hope this helps you

PE = mgh, solve for m

Answers

Answer:

P.E. = mgh, where m is the mass in kilograms,

Answer:

[tex]m = \frac{PE}{gh} [/tex]

Explanation:

[tex]if \: PE = mgh \\ then \to \\ m = \frac{PE}{gh} [/tex]

♨Rage♨



With some manipulation, the Rydberg equation can be rewritten in the form


E=constant×(1nf2−1ni2)


which allows you to calculate the energy of the emitted light. Express this constant in terms of the constants h, c, and RH using relationships between wavelength and energy as well as the Rydberg equation from the introduction.


Express the constant in terms of h and c, and RH.


Please help me with this question?

Answers

Answer:

attached below is the detailed solution

answer : value of constant = 2.18 * 10^-18 J

Explanation:

Express the constant in terms of h and c and RH

attached below is the detailed solution

Constant = [tex]h_{C} R_{H}[/tex]

               = ( 6.626 * 10^-34 ) * ( 3 * 10^8 ) * ( 1.097 * 10^7 )

               = 2.18 * 10^-18 J

The Planck equation and the light speed  allow us to find the results for the transformation of the Rydberg equation are:

   [tex]E = A ( \frac{1}{n_1^2}\frac{x}{y} - \frac{1}{n_2^2} )\\A= R_H \ h \ c \\A = 2.18 \ 10^{-18} j[/tex]

The Rydberg equation is an empirical expression that explains the wavelength of the emissions.

          [tex]\frac{1}{\lambda } = R_H ( \frac{1}{n_1^2} - \frac{1}{n_2^2} )[/tex]  

Where λ is the wavelength of the emitted radiation, is the Rydberg constant, n₁ and n₂ are integers with n₁ <n₂

It is asked to write the Rydberg equation  for the energy.

Let's use the Planck relation.

           E = h f

The light speed is related to the wavelength and frequency of radiation.

           c = λ f

           

Where E is the energy, h the Planck constant, c the speed of light, λ the wavelength and f the frequency.

Let's  substitute.

           E = [tex]\frac{hc}{\lambda}[/tex]  

           [tex]\frac{1}{\lambda} = \frac{E}{hc}[/tex]  

Let's substitute in the Rydberg equation.

          [tex]\frac{E}{hc} = R_H ( \frac{1}{n_1^2} - \frac{1}{n_2^2}) \\E = R_H \ h \ c \ ( \frac{1}{n_1^2} - \frac{1}{n_2^2} )[/tex]

We can write is an constant of the form.

          A = [tex]R_H h c[/tex]

The value of the constant is :          

          A = 1,097 10⁷ 6,626 10⁻³⁴ 3 10⁸

          A = 2.18 10⁻¹⁸ J

In conclusion, using the Planck equation and the light speed we can find the results for the transformation of the Rydberg equation are

        [tex]E = A ( \frac{1}{n_1^2} - \frac{1}{n_2^2} )\\ A = R_H h c\\[/tex]

       A = 2.18 10⁻¹⁸ J

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Does anybody understand this I’m stuck

Answers

Answer:

it's the first one

Explanation:

can you help me too

The answer is d I think

How many total atoms of element X are represented below?

Answers

It’s 4 on the left and 2 on the right so 6 altogether

Explain why warm air temperature has lower air pressure than cold air?

Answers

Answer:

Differences in temperature cause differences in air density. Warmer air is less dense than cold, which is why warm air tends to rise and cold air sinks.

temparature affects particles. warm particles are more spread out.

Explanation:

. Being acted on by gravity, colder, denser air weighs more and exerts greater pressure per unit area.

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