In my opinion I would say their mind is the most important tool, without it you can't use other tools.
Answer:
The conservation of momentum states that, within some problem domain, the amount of momentum remains constant; momentum is neither created nor destroyed, but only changed through the action of forces as described by Newton's laws of motion. ... Momentum is conserved in all three physical directions at the same time.
HBr is formed from hydrogen gas and bromine gas as shown in the reaction below;
H2(g) + Br2(g) = 2HBr(g)
The reaction involves bond breaking and bond formation
Decomposition of 1 mole of HBr requires 36.4kj/mol,
But, energy used in decomposition = energy used in formation
Thus, formation of a mole of HBr is -36.4 kj/mol
Therefore, formation of two moles of HBr would require
(-36.4 ×2) = 72.8
≈ -73 kj/mol
Hence, the enthalpy of formation of 2 moles of HBr (ΔH) is -73 kj/mol