một chất phóng xạ có chu kì bán hủy là 20 năm. Hỏi cần thời gian bao lâu để 25% và 75% lượng chất đó bị phân hủy? sau 60 năm bao nhiêu phần trăm chất đó bị phân hủy ?

Select the correct answer. you have a nightlight plugged into an outlet in the hallway, which uses 3.5 watts when plugged in. if the house circuit provides 120.0 volts, what is the current through this bulb?

Why do you suppose the structural polysaccharide cellulose does not contain branches? why do you suppose the structural polysaccharide cellulose does not contain branches? branches in the molecule would generate side chains that would almost certainly make it difficult to pack the cellulose molecules into globules, thereby decreasing the flexibility and strength of the globules. branches in the molecule would generate side chains that would almost certainly make it difficult to pack the cellulose molecules into microfibrils, thereby increasing the rigidity and strength of the microfibrils. branches in the molecule would generate side chains that would almost certainly make it difficult to pack the cellulose molecules into globules, thereby increasing the flexibility and strength of the globules. branches in the molecule would generate side chains that would almost certainly make it difficult to pack the cellulose molecules into microfibrils, thereby decreasing the rigidity and strength of the microfibrils.

Abeaker with 2.00×102 ml of an acetic acid buffer with a ph of 5.000 is sitting on a benchtop. the total molarity of acid and conjugate base in this buffer is 0.100 m. a student adds 4.70 ml of a 0.360 m hcl solution to the beaker. how much will the ph change? the pka of acetic acid is 4.740.