Question

please show all calculations to find (a) wood floats on water because it is less dense. If a cubic piece of metal has sides of 1.25 cm and a mass of 37.7 g will the metal float on a pool of mercury (b) Convert 15. g Ba(NO₃)₂ to formula units (c) what mass is equal to 63.2 mmol of benzoic acid, C₇H₆O₂?

Answer 1

(a) Density of mercury is 13.56 g/cm³

Volume of the metal , V = side³ = (1.25 cm)³ = 1.95 cm³

Mass of metal , m = 37.7 g

So density of metal , d = mass/volume

                                 = 37.7g / 1.95 cm³

                                = 19.3 g/cm³

So the density of metal is more than that of mercury it will not float on a poll of mercury

(b) Mass of Ba(NO3)2 is 15 g

Molar mass of Ba(NO3)2 is 261.34 g/mol

So number of moles of Ba(NO₃)₂ , n = mass/molar mass

                                                     = 15 g / 261.34(g/mole)

                                                     = 0.057 moles

(c) Mass of benzoic acid , m = number of moles x molar mass

                                          = 63.2 mmole x 10^-3 mol/mmole x 122.12 g/mole

                                          = 7.718 g