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2 years ago

Unknown element x has four energy levels, five valence electrons, and is a metalloid. what is elements x?

Chemistry

1 answer:

kykrilka [37]2 years ago

8 0

Answer:

Element X is Arsenic (As)

Explanation:

Elements in the periodic table are either metals, non-metals or metalloids.
Metals are elements that react by losing electrons to obtain a stable configuration and form cation.
Non-metals are those elements that react by gaining electrons to form a stable configuration and form anion.
Metalloids are elements in the periodic table that have both metallic and non-metallic properties.
Examples of metalloids include Selenium, Arsenic, Boron, etc.
Arsenic is a metalloid in period 4 (four energy levels) with five valence electrons.

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How many molecules of CBr4 are in 250 grams of CBr4

Kazeer [188]

Answer:- $4.54*10^2^3$ molecules.

Solution:- The grams of tetrabromomethane are given and it asks to calculate the number of molecules.

It is a two step unit conversion problem. In the first step, grams are converted to moles on dividing the grams by molar mass.

In second step, the moles are converted to molecules on multiplying by Avogadro number.

Molar mass of $CBr_4$ = 12+4(79.9) = 331.6 g per mol

let's make the set up using dimensional analysis:

$250g(\frac{1mol}{331.6g})(\frac{6.022*10^2^3molecules}{1mol})$

= $4.54*10^2^3$ molecules

So, there will be $4.54*10^2^3$ molecules in 250 grams of $CBr_4$ .

8 0

1 year ago

Approximately what volume do 3.0 moles of kr gas occupy at stp? 80.0 40.0 l none of the above 20.0

podryga [215]

None of the above.
1 mole filled with gas at STP occupies
=22.4 L

∴ 3mole of kr gas at STP occupies
= 3 × 22.4
= 67.2 L

4 0

2 years ago

Read 2 more answers

Caffeine, a molecule found in coffee, tea, and certain soft drinks, contains C, H, O, and N. Combustion of 10.0 g of caffeine pr

denis-greek [22]

Answer:

194 g/mol.

Explanation:

Hello,

In this case, one first must compute the mass of each element as shown below:

$C=18.13gCO_2*\frac{12gC}{44gCO_2} =4.945gC\\H=4.639gH_2O*\frac{2.016gH}{18.0152gH_2O}=0.519gH\\N=2.885gN_2\\O=10.0g-4.945g-0.519g-2.885g=1.651gO$

Next, the corresponding moles:

$C=4.945gC*\frac{1molC}{12gC}=0.412mol\\H=0.519gH*\frac{1molH}{1gH}=0.519mol\\N=2.885gN*\frac{1molN}{14gN}=0.206molN\\O=1.648gO*\frac{1molO}{16gO} =0.103molO$

Then, each element's subscripts is found to be:

$C=\frac{0.412}{0.103}=4\\H=\frac{0.519}{0.103}=5\\N=\frac{0.206}{0.103} =2\\O=\frac{0.103}{0.103}=1$

Therefore, the empirical formula is:

$C_4H_5N_2O$

Nonetheless, it has a molar mass of 97bg/mol, thereby, by multiplying such formula by 2 one gets:

$C_8H_10N_4O_2$

Which has a molar mass of 194 g/mol being correctly contained in the given interval.

Best regards.

8 0

2 years ago

Which phrase best describes a chemical reaction? A. mixing two substances B. the combustion of a substance C. forming or breakin

nirvana33 [79]

The answer for the problem is C

6 0

2 years ago

Read 2 more answers

Avogadro’s number was calculated by determining the number of atoms in 12.00 g of carbon-12. 14.00 g of carbon-12. 12.00 g of ox

OLga [1]

Answer:

Avogadro’s number was calculated by determining the number of atoms in 12.00 g of carbon-12.

Explanation:

The number of particles presents in one mole of a substance is known as Avogadro's number.

Avogadro's number is $6.022\times10^2^3$ atoms or molecules or ions or particles present in one mole of a substance. It is denoted by the symbol $L$ or $N_A$ . It is a dimensionless quantity.

Avogadro's number was proposed by Jean Perrin but named in the honor of italian scientist Amedeo Avogadro.

Avogadro's number is the number of atoms present in 12 grams of carbon-12.

8 0

2 years ago

Read 2 more answers