How many grams of water react to form 4.50 moles of Mg(OH)2?
MgO(s) + H20(1)
Mg(OH)2(s)

mass of water is 81.1 g

Explanation: from reaction eguation you see there are equal amounts of water and Mg(OH)2. Then amount of water is 4.50 mol. Molar mass of water is 18.016 g/mol.

Mass m= n·M= 4.50 mol· 18.016 g/mol = 81.1 g

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