Science! please help does anyone know this

b- destructive interference that results in a lower amplitude

c- destructive interference that results in a greater frequency

d- constructive interference that results in a lower frequency

How many moles are in 43.9 l of oxygen

Cryolite, na3alf6(s), an ore used in the production of aluminum, can be synthesized using aluminum oxide. start this question by first balance the chemical equation.1.) balance the equation: - alo3(s)+naoh(l)+hf(> na3alf6+h2o(g). 2.) if 17.5 kilograms of al2o3(s), 51.4 kilograms of naoh(l), and 51.4 kilograms of hf(g) react completely, how many kilograms of cryolite will be produced? 3.)which reactants will be in excess, (al2o3, naoh, or hf) 4.)what is the total mass of the excess reactants left over after the reaction is complete in kg?

Asample of hydrated tin (ii) chloride (sncl2) has a mass of 4.90 g. when it is dehydrated, it has a mass of 4.10 g. which is the correct chemical formula for the hydrate? sncl2•2h2o          sncl2•4h2o          sncl2•6h2o