All categories

3 years ago

Who discovered copper

Chemistry

2 answers:

Komok [63]3 years ago

7 0

Explanation:

The exact person is unkown cooper has been around for ages since 9000 BC in the Middle East are the earliest discoveries

sesenic [268]3 years ago

5 0

Although various copper tools and decorative items dating back as early as 9000 BCE have been discovered, archaeological evidence suggests that it was the early Mesopotamians who, around 5000 to 6000 years ago, were the first to fully harness the ability to extract and work with copper

You might be interested in

Limiting Reactants—————-

denis-greek [22]

Answer:

21.8 grams.

Explanation:

Molar mass data from a modern periodic table:

Mg: 24.301;
O: 15.999.

How many moles of MgO will be produced if Mg is the limiting reactant?

Number of moles of Mg:

$\displaystyle n = \frac{m}{M} = \frac{16.3}{24.301} = 0.670644\;\text{mol}$ .

The ratio between the coefficient of Mg and that of MgO is 2:2. Two moles of Mg will make two moles of MgO. 0.670644 moles of MgO will be produced if Mg is the limiting reactant.

How many moles of MgO will be produced if O₂ is the limiting reactant?

Number of moles of O₂:

$\displaystyle n = \frac{m}{M} = \frac{4.33}{15.999} = 0.270642\;\text{mol}$ .

The ratio between the coefficient of O₂ and that of MgO is 1:2. One mole of O₂ will make two moles of MgO. $2\times 0.270642 = 0.541284\;\text{mol}$ of MgO will be produced if O₂ is in excess.

How many moles of MgO will be produced?

0.541284 is smaller than 0.670644. Only 0.541284 moles of MgO will be produced since O₂ will run out before all 16.3 grams of Mg is consumed.

What's the mass of 0.541284 moles of MgO?

Formula mass of MgO:

$24.301 + 15.999 = 40.300\;\text{g}\cdot\text{mol}^{-1}$ .

Mass of 0.541284 moles of MgO:

$m = n \cdot M = 0.541284\times 40.300 = 21.8\;\text{g}$ .

7 0

3 years ago

What is the pOH of a solution with [OH'] = 9,0 x 10-7?

bearhunter [10]

Answer: D (6.04) is the best answer

Explanation:

pOH = - log [OH⁻]

pOH = - log (9.0 x 10⁻⁷)

pOH = 6.0457

6 0

3 years ago

Which statements accurately describe volume? Check all that apply.

lesantik [10]

Where is the chooses for you question

8 0

3 years ago

Sighting along the C2-C3 bond of 2-methylbutane, the least stable conformation (Newman projection) has a total energy strain of

natima [27]

Answer:

21 KJ/mol

Explanation:

For this question, we have to start with the linear structure of 2-methylbutane. With the linear structure, we can start to propose all the Newman projections keep it in mind that the point of view is between carbons 2 and 3 (see figure 1).

Additionally, we have several energy values for each interaction present in the Newman structures:

-) Methyl-methyl gauche: 3.8 KJ/mol

-) Methyl-H eclipse: 6.0 KJ/mol

-) Methyl-methyl eclipse: 11.0 KJ/mol

-) H-H eclipse: 4.0 KJ/mol

Now, we can calculate the energy for each molecule.

Molecule A

In this molecule, we have 2 Methyl-methyl gauche interactions only, so:

(3.8x2) = 7.6 KJ/mol

Molecule B

In this molecule, we have a Methyl-methyl eclipse interaction a Methyl-H eclipse interaction and an H-H eclipse interaction, so:

(11)+(6)+(4) = 21 KJ/mol

Molecule C

In this molecule, we have 1 Methyl-methyl gauche interaction only, so:

3.8 KJ/mol

Molecule D

In this molecule, we have three Methyl-H eclipse interaction, so:

(6*3) = 18 KJ/mol

Molecule E

In this molecule, we have 1 Methyl-methyl gauche interaction only, so:

3.8 KJ/mol

Molecule F

In this molecule, we have a Methyl-methyl eclipse interaction a Methyl-H eclipse interaction and an H-H eclipse interaction, so:

(11)+(6)+(4) = 21 KJ/mol

The structures with higher energies would be less stable. In this case, structures B and F with an energy value of 21 KJ/mol (see figure 2).

I hope it helps!

3 0

3 years ago

Use this information to determine the number of valence electrons in the atoms. Which of the following correctly compares the st

vlabodo [156]

The question is incomplete. The complete question is :

The table compares the number of electrons in two unknown neutral atoms.

Comparison of Electrons

Atom Number of Electrons

A 9

D 11

Use this information to determine the number of valence electrons in the atoms. Which of the following correctly compares the stability of the two atoms?

A. Both are unreactive.

B. Both are highly reactive.

C. A is unreactive and D is reactive.

D. A is reactive and D is unreactive.

Answer:

B. Both are highly reactive.

Explanation:

Atomic number of electrons given is 9 and 11, it means that atom A is fluorine (F) and atom D is Sodium (Na).

In order to gain stability 8 electrons are required in outer shell. So atoms either gain or lose electrons in its outer shell to become more reactive.

Sodium has electronic configuration (2,8,1) and easily loses one electron and become (2, 8) which is highly reactive.

Fluorine has electronic configuration (2, 7) and can gain easily an electron and becomes reactive to form (2, 8).

So, both they both attain stability by losing and gaining only one electron.

Hence, they both are highly reactive and the correct option is B.

8 0

3 years ago