Answer:
3.43 %
Explanation:
We need to calculate first the number of moles of CeO2 produced in the combustion. Given its formula we know how many moles of Ce atom are present. From there calculate the mass this number of moles this represent and then one can calculate the percentage.
0.1848 g CeO2 x 1 mol CeO2/172.114g = 0.00107 mol CeO2
0.00107 mol CeO2 x 1 mol Ce/ 1 mol CeO2 = 0.00107 mol Ce
.00107 mol Ce x 140.116 g Ce/ mol = 0.150 g Ce
0.150 g Ce/ 4.3718 g sample x 100 = 3.43 %
No, the elements are not always transparent.
<u>Explanation:</u>
The elements become transparent when the light passes through those elements. Transparency is caused because of the transmission and the passing of the light waves through these elements.
But the metals do not become transparent even when the light waves pass through these metals. Metals do not become transparent because the refractive index in them is very big.
Use M x V = M' x V'
0.300 x V = 0.100 x 250
V = .......... ml
Answer is "0.05 mol".
<em>Explanation;</em>
We can do calculation by using a simple formula as
n = m/M
Where, n is the number of moles of the substance (mol), m is the mass of the substance (g) and M is the molar mass of the substance (g/mol).
Here,
n = ?
m = 2.80 g
M = 56.08 g/mol
By substitution,
n = 2.80 g /56.08 g/mol
n = 0.0499 mol ≈ 0.05 mol