At 25°C, hydrogen iodide breaks down very slowly to hydrogen and iodine: rate = k[Hlf The rate constant at 25°C is 2.4X 10-21 L/mol-s. If 0.0100 mol of HI(g) is placed in a 1.0-L container, how long will it take for the con­centration of HI to reach 0.00900 mol/L (10.0% reacted)?

The answer is 5 10 15

    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