How many moles are in 6.21x1025 atoms of magnesium oxide?

55.56 moles of MgO

Explanation:

1 mole = avogadro number

if 6.21x10^25 atoms then molecules of MgO (equal numbers of Mg and O atoms)

= 0.5*6.21x10^25 = 3.105 molecules of MgO

So moles of MgO = 0.5*6.21*10^25/avogadro number = 55.56

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance

answer: e.   sour taste

explanation: acids are those substances which dissociates in water to give ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. acids are sour in taste. example: hcl

bases are those substances which dissociates in water to give ions or accepts ions. as they dissociate to give ions, they act as electrolytes and thus are electrically conductive. bases are bitter in taste. bases are slippery in nature.