Use the Nernst equation to calculate the theoretical value of E of th copper-concentration cell and compare this value with th cell potential you measured. E = E* - 0.0592 / n * logQ

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.

Density= mass/volume so 5.1 divided by 4.7 is  5.1 / 4.7 =1.08510638298round to the correct number of sig figs