A chemistry graduate student is given 300. mL of a 0.20 M ammonia (NH_3) solution. Ammonia is a weak base with K_b = 1.8 times 10^-5. What mass of NH_4 Br should the student dissolve in the NH3 solution to turn it into a buffer with pH = 9.10? You may assume that the volume of the solution doesn't change when the NH4Br is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits.

Two people each hold the end of a rope and create waves by moving their arms up and down. this wave is best classified as a transverse wave because a) both the rope particles and the wave are moving in the same direction. b) the wave is moving up and down as the particles of the rope move horizontally. c) the wave is moving horizontally as the particles of the rope move up and down. eliminate d) the wave is moving in a parallel direction with the motion of the person's arms.