How many moles of HCl need to be added to 200.0 mL of a 0.200 M solution of NaF to make a buffer with a pH of 2.80? (Ka for HF is 6.8 × 10⁻⁴)

Which of these describes how heat is transferred by convection* a. sunlight travels through space without the aid of fluids or solids. b. warm air rises and takes the heat with it, eventually, it cools and sinks c. air at the equator rises and sinks at the poles. d. air molecules touch the warm ground, heating them up *not conduction