The reaction only takes place if the reactants are in contact, then the surface exposed is very important because as the exposed surface of the reactants increases, the reaction velocity also increases. If the lumps are not broken up, a big amount of baking soda would be only available to react after the surrounding soda has already reacted.
the variations in riser height or tread depth should not be grater than that is equal to 9.5 mm but the maximum riser height should be the but variation in riser height should not exceed to . The minimum riser height should be 7 inches which is equal to the 178 mm