The molar mass of ba(oh)2 is
(1) 154.3 g (3) 171.3 g
(2) 155.3 g (4) 308.6 g

Ba(OH)₂ = 137.3 + 16 x 2 + 1 x 2 = 171.3 g

Answer (3)

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Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.