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3 years ago

Which elements have 8 valence electrons?

2 answers:

6 0

Any element in group 18 has eight valence electrons (except for helium, which has a total of just two electrons). Examples include neon (Ne), argon (Ar), and krypton (Kr). if that’s what u mean

notka56 [123]3 years ago

6 0

Answer:

Any element in group 18 has eight valence electrons (except for helium, which has a total of just two electrons). Examples include neon (Ne), argon (Ar), and krypton (Kr).

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I have my chemistry EOC tomorrow, and I need to know how to calculate the molar mass of a compound. Specifically ones set up lik

yuradex [85]

Answer:

357.475

Explanation:

First you need periodic table and you have to look for mass

Fe = 3 x 55.845 = 167.535

P = 2 x 30.97 = 61.94

o = 4 x 2 so 8 oxygen = 8 x 16 = 128

add all and you get 357.475

6 0

3 years ago

If 1.0 mole of neon, 2.0 moles of helium, and 3.0 moles of argon are mixed, what is the mole fraction of helium?

alexandr1967 [171]

The mole fraction of helium is 0.33.

The mole fraction can be calculated with the aid of dividing the number of moles of 1 factor of an answer by means of the overall number of moles of all the additives of a solution. it's far noted that the sum of the mole fraction of all the components in the solution should be same to one.

Mole fraction is a unit of attention. within the answer, the relative amount of solute and solvents are measured by the mole fraction and it is represented. The mole fraction is the wide variety of moles of a specific thing within the solution divided by way of the entire wide variety of moles.

Mole fraction represents the quantity of molecules of a selected thing in a combination divided by using the total variety of moles within the given mixture. it is a manner of expressing the concentration of a solution. consequently, the sum of mole fraction of all of the additives is always equal to one.

Mole of neon = 1

mole of helium = 2

mole of argon = 3

Total mole = 1 + 2 + 3 = 6

Mole fraction = mole of helium / total mole

= 2 / 6 = 0.33

Learn more about mole fraction here:-brainly.com/question/1601411

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7 0

1 year ago

When one metal mixes into the crystalline lattice of another it is called a(n) alloy compound chemical reaction heterogeneous so

bekas [8.4K]

the correct answer is alloy

6 0

3 years ago

Which of the following reactions have a positive ΔSrxn? Check all that apply.

PolarNik [594]

Answer:

The reactions that have a positive ΔS rxn are the first and the fourth choices:

2A(g) + B(s) → 3C(g)

2A(g) + 2B(g) → 5C(g)

Explanation:

ΔS rxn is the change of entropy of the chemical reaction.

ΔS rxn = S after reaction - S before reaction.

Therefore, a positive ΔS rxn means that the entropy after the reaction is greater than the entropy before the reaction.

You may use some assumptions to predict whether a reaction will lead an increase or decrease of the entropy.

First, assume that all the non-shown conditions, such as temperature and pressure, are constant.

Under that assumption, and from the meaning of entropy as a measure of the disorder or randomness of a system you can predict the sign of the change of entropy.

2A(g) + B(s) → 3C(g)

1) The solid compounds, B(s) in this case, are very ordered and so they have low entropy.

2) Gas molecules are highly disordered (scattered), and the greater the number of molecules of the gas the larger the entropy, S).

Hence, since the product side shows 3 gas molecules and the reactant side shows 2 gas molecules and 1 solid molecule, you predict that the products have a larger entropy than the reactants, meaning an increase in entropy: ΔS rxn is positive.

2A(g) + B(g) → C(g)

Using the same reasoning, 3 gas molecules in the reactant side have more entropy than 1 molecule in the product side, and so the reaction leads to a decrease in the entropy: ΔS rxn is negative

A(g) + B(g) → C(g)

Again, 2 gas molecules in the reactant side have more entropy than 1 molecule in the product side, and so the reaction leads to a decrease in the entropy: ΔS rxn is negative

2A(g) + 2B(g) → 5C(g)

With the same reasoing, 5 molecules in the product side, lets you predict that will have more entropy than 4 molecules in the reactant side, and, the entropy will increase: ΔS rxn is positive.

6 0

3 years ago

A cylindrical glass tube of length 27.4cm and radius 4 cm is filled with gas. The empty tube has a mass of 254.3 g. The tube fil

Temka [501]

Density of the gas is 3.05 × 10⁻³ g / cm³.

Explanation:

Volume of the cylinder = π r² h

where r is the radius and h is the height of the height or the length of the glass tube.

Here r = 4 cm and h = 27.4 cm

Volume of the cylinder = 3.14 × 4 × 4 × 27.4 = 1376.6 cm³

We have to find the mass of the gas by subtracting the mass of the tube filled with the substance from the mass of the empty tube.

Mass of the substance = 258.5 - 254.3 = 4.2 g

We have to find the density using the formula as,

$$ Density = \frac{mass}{volume}$

Plugin the values as,

$$ Density = \frac{4.2}{1376.6}$

= 3.05 × 10⁻³ g / cm³

So the Density of the gas is 3.05 × 10⁻³ g / cm³.

3 0

3 years ago