Answer:
Empirical Formula: 
Explanation:
Since total mass is 306, we have:
Mass of $Al = \frac{52.9}{100}\times 306=161.87 $
Mass of $O= \frac{47.1}{100}\times 306=144.126$
Hence,
Moles of $Al=\frac{Mass}{molar mass}=\frac{161.87}{27}=6$
Moles of $O= \frac{Mass}{molar mass}=\frac{144.126}{16}=9$
Hence the formula is $Al_6O_9$ , or, $Al_2O_3$
D - density: 40 mg/ml
V - volume: 175 ml
m - mass: ??
__________
d = m/V
m = V×d
m = 175×40
m = 7000 mg = 7 g
:•)
Hydrogen gas
Calcium + Water. In the following demonstration, a chunk of calcium metal is dropped into a beaker of distilled water. After a second or so, the calcium metal begins to bubble vigorously as it reacts with the water, producing hydrogen gas, and a cloudy white precipitate of calcium hydroxide.
E = hf
c = speed of electromagnetic wave, c ≈ 3 * 10⁸ m/s,
Planck's constant h = 6.63 *10⁻³⁴ Js
h = Planck's constnat, Frquency, f = c/λ = (3*10⁸)/(488*10⁻⁹)
E = hf
E = hc/λ
E = (6.63 * 10⁻³⁴ * 3 * 10⁸) /(488 * 10⁻⁹)
Energy, E ≈ 4.0758 * 10⁻¹⁹ Joules.
