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Which of the following numerical expressions gives the number of moles in 5.0g of CaO ?



5.0g×56g/mol


A


5.0g56g/mol


B


56g/mol5.0g


C


15.0g×156g/mol

Respuesta :

Answer:

The expression for the number of moles is 5.0 g / 56 g/mol

Explanation:

The mole is the amount of substance that contains as many entities as there are carbon atoms in 12 grams of a carbon-12 isotope. It is the amount of a substance that contains the same number of units as the number of atoms in 12g of carbon - 12 isotope. A mole of an ionic substance contains 6.02 * 10^23 atoms of the element. Mathematically, moles is the mass of a substance in grams divided by the relative molecular mass.

Moles = mass / relative molecular mass

In the given question, mass = 5.0 g

Molecular mass of CaO  ( Ca= 40, O = 16) = ( 40 + 16) g/mol = 56 g/mol

Moles = 5.0 g/ 56 g/mol is the expression for the number of moles in 5.0 g of CaO

CintiaSalazar

Answer:

Explanation:

Taking into account the definition of mal and mass molar,

The mole is defined as the amount of matter that contains a certain number of elementary entities (which can be an atom, molecule, ion, electron, or any other particle or a specific group of such particles) equivalent to the number of atoms in 12 grams of the carbon-12 isotope.

In other words, the mole is the amount of substance that contains as many particles (atoms, molecules, ions, etc.) as there are in 12 g of the isotope of carbon 12. A mole of any compound always contains a number of molecules equal to the number by Avogadro (6.023×10²³).

On the other hand, molar mass is the amount of mass that a substance contains in one mole and is expressed in g/mole.

In this case, the molar mass of CaO being 56 g/mole, the amount of moles in 5 g of the compound can be calculated by means of the expression:  

5.0 g/ 56 g/mol

Finally, the correct answer is second option.

Learn more about mol and mass molar:

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