15. Consider the following hypothetical reduction half reactions shown below: X2+(aq) + 2e- → X(s) Ereduction = +2.15 V Y1+ (aq) + e →Y(s) Eºreduction = -0.55
Z3+ (aq) + 3e- → Z(S) V Eºreduction = -1.42 V

Which of the following reactions, if any, will occur?
1. Z(S) + 3Y1+(aq) → 3Y(s) + Z3+ (aq)
II. 3X(S) + 273+(aq) 2Z(s) + 3X2+ (aq)
III. X2+(aq) + 2Y(s) → 2Y1+(aq) + X(S)
IV. Y(S) + Z3+ (aq) → 3Y1+(aq) + Z(S)

a. I only
b. II and IV only
c. I and III only
d. I, II and III only

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

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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.