Question

Find the number of atoms in a copper rod with a length of 9.90 cm and a radius of 1.00 cm. The density of copper is 8.96 g/cm3 Express the number of atoms to three significant figures or x ion 芻 2.64 1022 Cu atoms Submit Previous Answers Request Answer X Incorrect; Try Again; 5 attempts remaining
Please help! I got this wrong. Please show work too. Thank you!

Answer 1

First we calculate the volume of rod using given information as v = pi r^2 h rightarrow (01) where v = volume r = radius = 1 cm h = height (or) length = 9.90 cm pi = constant = 3.14 putting this value in above eq^n (1) we get v = 3.14 times (1)^2 times 9.90 cm v = 3.14 times 1 cm times 9.90 cm v = 31.086 c m^3 Inserting this value of volume in density equation we get d = m/v rightarrow (02) d = density m = mass (m) v = volume Rearranging eq^n (02) for mass m = d times v putting given value is above rearranged eq^n m = 8.96 g/cm^3 times 31.086 \r\n m = 278.53 g moles of copper moles = mass (g)/molar mass = 278.537/63.54 g/mole = 4.383 moles of cu