Cesium-137 has a half-life of 30 years. you find a sample with 3 g of cesium-137. how much cesium-137 existed in the sample 90 years ago?

If a polyatomic ionic compound has gained two hydrogen ions, then how does its name begin?

Answer asap need to be answered by wednesday morning explain how a buffer works, using an ethanoic acid / sodium ethanoate system including how the system resists changes in ph upon addition of a small amount of base and upon addition of a small amount of acid respectively. include the following calculations in your i. calculate the ph of a solution made by mixing 25cm3 0.1m ch3cooh and 40cm3 0.1m ch3coo-na+. [ka = 1.74 x 10-5 m] ii. calculate the ph following the addition of a 10cm3 portion of 0.08 m naoh to 500cm3 of this buffer solution. iii. calculate the ph following the addition of a 10cm3 portion of 0.08 m hcl to 200cm3 of the original buffer solution.

The number of moles of a given mass of a substance can be found without knowing its molecular formula or molar mass. true false