What describes using organisms that were only alive during a specific time period to estimate the unknown age of items

A radioactive dating
B law of superposition
C relative dating
D index fossil

Answer:

The correct option is Malachite which has both copper nd oxygen.

Explanation:

As we the symbol of copper is Cu while the symbols of oxygen is O. As the chemical formula of malachite is Cu₂CO₃(OH)₂. So it has Cu as well as O.

Glucose has only oxygen but no copper

Chalcopyrite has copper but no oxygen

Calcite has oxygen but no copper.

So correct answer is only malachite.

pls give brainlist

Cl refer to chlorine atoms. They don't exist naturally in that form. Rather, Cl2 refer to chlorine molecules, and they exist as that form in nature.

Answer:

2.09 moles

Explanation:

1 mole=6.022*10^23 moles --> 1.26×10^(24)/(6.022*10^23)=2.09 moles

Answer:

2Fe₂O₃

Explanation:

If the number of atoms of each element are the same on reactant and product sides, it is a balanced equation. This is not a balanced equation because the number of atoms of each element are not the same on reactant and product sides.

To balance an equation, let's first list the atoms:

Then, we count the number of atoms on both sides:

We multiply the number of atoms for each element on either side by the number of molecules (aka coefficient, or "big number"):

To balance the equation, we need the total number for Fe on the right side to be 4, and the total number for O on the right side to be 6. We can do that by adding a "big number", or coefficient in front, which when multiplied by the number of atoms for each element, makes a balanced equation.

2 is a good value: 2 × 2 = 4, and 2 × 3 = 6.

As such:

4Fe + 3O₂ → 2Fe₂O₃

Answer:

34.6g

Explanation:

Given parameters:

Mass of Octane  = 11.2g

  Reaction expression;

      2C₈H₁₈  + 25O₂  →  16CO₂  + 18H₂O

Mass of octane = 11.2g

Unknown:

Mass of carbon dioxide produced  = ?

Solution:

From the balanced reaction equation;

         2 mole of octane produced 16 moles of carbon dioxide

From the given specie, let us find the number of moles;

    Number of moles  = [tex]\frac{mass}{molar mass}[/tex]  

 Molar mass of C₈H₁₈   = 8(12) + 18(1) = 114g/mole

Number of moles of octane  = [tex]\frac{11.2}{114}[/tex]   = 0.098mole

    2 mole of octane produced 16 moles of carbon dioxide

    0.098 mole of octane will produce [tex]\frac{0.098 x 16}{2}[/tex]   = 0.79mole of CO₂

Mass of CO₂ = number of moles x molar mass

           Molar mass of CO₂ = 12 + 2(16)  = 44g/mol

Mass of CO₂  = 0.79 x 44  = 34.6g

Probably the two elements with properties most like beryllium are magnesium and aluminum.

According to the electronic configuration elements that will react similarly to beryllium  are magnesium and calcium.

Electronic configuration is defined as the distribution of electrons which are present in an atom or molecule in atomic or molecular orbitals.It describes how each electron moves independently in an orbital.

Knowledge of electronic configuration is necessary for understanding the structure of periodic table.It helps in understanding the chemical properties of elements.

Elements undergo chemical reactions in order to achieve stability. Main group elements obey the octet rule in their electronic configuration while the transition elements follow the 18 electron rule. Noble elements have valence shell complete in ground state and hence are said to be stable.

Learn more about electronic configuration,here:

https://brainly.com/question/29757010

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Answer:

Physical

Explanation:

When something melts it is still the same substance.

For example:

Ice and water are still both water, so that would be a physical change.

If a reaction changes the substance into a new/different substance then it is a chemical change.