This symbol < – –> indicates:
a. that heat must be applied.
b. that the reaction is reversible.
c. an incomplete combustion reaction.
d. that a gas is formed by the reaction.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

there are two significant figures.

the answer is yes

it has kinetic energy

reason

an object has kinetic energy when you stop the force carrying it, the object will stay in motion.

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nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.