Answer:
6.95 x 10²³ molecules/particles
Step-by-step explanation:
First we need to find the total Empirical Mass. We can find this by adding each element's mass together.
Al = 26.982,
O = 15.999
H = 1.008
26.982 + 3(15.999) + 3(1.008) = 78.003.
Now we divide by the mass given (90 grams).
90/78.003 = 1.153801777.
We then take that number and multiply it by avogadro's number (6.022 x 10²³)
1.153801777 x avogadro's number = 6.95 x 10²³