Answer to Question #89003 in General Chemistry for beth

Question

how many atoms of copper are there in a piece of copper that weighs the same as a piece of aluminum that contains 4.86 x 10(21) atoms of aluminum

Answer 1

Let's find out the amount of Aluminium.

n = N_Al / N_A = 4.86 × 10²¹ / 6,02 × 10²³ = 0.807 × 10^-2 (mol);

Now we can find out the mass of Aluminium:

m_Al = n × Mr = 0.807 × 10^-2 × 27 = 0.218 (g);

As the masses of Aluminium and Copper are equal, we can calculate the amount of Copper:

n = m_Cu / Mr = 0.218/64 = 0.0034 (mol);

N_Cu = n × N_A = 0.0034 × 6.02 × 10²³ = 2.05 × 10²¹