Calcium reacts with a transition metal to form a compound with the general formula Ca(X). What would be the most likely formula for the compound formed between potassium and the polyatomic ion X?
A) K X
B) K2X
C) KX2
D) K2X3
E) K3X2

answer; ///i do believe that the correct answer is (b); ///particle composed of two or more atoms bonded together;

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.