Calculate the mass per cent of different elements present in sodium sulphate (Na2so4).​

Can someone me with 1 to 4 plz. fast

In water, a strong acid will break down into its component parts. a. completely b. partly c. never in water, a weak base will break down into its component parts. a. completely b. partly c. never

Which theory was contradicted by experiments with the photoelectric effect? light spreads out after it passes through a small opening. as soon as light strikes metal, electrons will be ejected. visible light, regardless of color, will cause the ejection of electrons when striking metal. the kinetic energy of ejected electrons depends on the frequency of light that strikes the metal.