48. 227Ac has a half-life of 21.8 years. How long will it take for a sample of 227Ac to reach
a
20.0% of its initial amount?

What is the composition, in atom percent, of an alloy that consists of 4.5 wt% pb and 95.5 wt% sn? the atomic weights for pb and sn are 207.19 g/mol and 118.71 g/mol, respectively.(a) 2.6 at% pb and 97.4 at% sn(b) 7.6 at% pb and 92.4 at% sn(c)97.4 at% pb and 2.6 at% sn(d) 92.4 at% pb and 7.6 at% sn

22. a flask containing 450 ml of 0.50 m h2so4 was accidentally knocked to the floor. how many grams of nahco, do you need to put on the spill to neutralize the acid according to the following equation: h2so4(aq)+2 nahcos(aq) na, so(aq) +2 h20()+2 co2(g) d) 38 g a) 2.3 g b) 9.5 g c) 19 g

Calculate the frequency of a wave in a spring toy. the wave has a speed of 1.1 meters per second and a wavelength of 0.1 meters. *