What is one "requirement" or thing that the rescue workers MUST have for their energy source? Think about the original problem. Plz Help Me

    pb(so₄)₂this element is lead (iv) sulfate. lead is a multivalent ion. but we know that sulfate ions, so₄²⁻, have a charge of -2. in order to have the ratios match up, we need pb⁴⁺ (two times as many pb⁴⁺  than so₄²⁻).the molar mass can be calculated by finding the mass of one mole of this compound. consider the following calculation,  where amu represents the atomic mass unit. the amu for each atom involved in this compound can be found on a periodic table.  molar mass = amu pb + 2(amu s + 4 * amu o)from a periodic table (with masses rounded to the nearest tenth),      amu pb = 207.2 g    amu s =  32.1 g    amu o = 16.0 gtherefore    molar mass =  207.2 + 2(32.1 + 4*16.0) = 399.4 gthe molar mass is therefore 399.4 grams per mol

If each of the reactants have 2 elements it is usually double displacement. when there is double displacement, if one reactant has hydrogen then it can be acid base. if one reactant has 2 and one has 1, than it is usually single displacement. if there is only one reactant it is decomposition. if there are two reactants that each have one element it is synthesis. if one of the reactants is 02 it can be combustion and the products has to include h20 and c02.