What is true for the following reaction? ca(s) + 2c(s) cac2(s) + 62.8 kj it is an endothermic reaction and ∆h= +62.8 kj. it is an endothermic reaction and ∆h= -62.8 kj. it is an exothermic reaction and ∆h= +62.8 kj. it is an exothermic reaction and ∆h= -62.8 kj. this reaction will not occur.

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

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation: