второе---
первое--- 2СН4 = С2Н2 + 3Н2 С2Н2 + 2Н2 = С2Н6 С2Н6 + Сl2 = С2Н5Сl + НСl С2Н5Сl + NaOH = С2Н4 + NaСl + Н2О
третье--------CaC2 + H2 = Ca + C2H2 C2H2 + H2 = C2H4 C2H4+HBr=C2H5Br C2H5Br + Na = C4H10 + NaBr
четвертое---
CH4 + Cl2 = CH3Cl + HCl
CH3Cl + KOH = CH3OH + KCl
CH3OH + CuO = CH3CHO + Cu + H2O