What method will speed up a chemical reaction? apply heat
avoid grinding the substance
decrease the concentration of the reactants

The correct  answer is "apply heat". A method that will speed up a chemical reaction is to apply heat. Energy is directly proportional to kinetic energy which is the energy of motion. Increasing the heat will promote the molecules to move faster therefore colliding more to the molecules in the system resulting to a faster reaction.

Not a  mixture of two common elements that can be separated by physical means.

Answer:             1.0  × 10⁻⁵ msolution:                     as we know ph is given as,                                    ph  = -log [h⁺]and,                                    [h⁺]  =  10^-ph    (1)putting value of ph in eq. 1,                                    [h⁺]  =  10⁻⁵                                    [h⁺]  =  1.0  × 10⁻⁵ m