It's a cube so the volume = edge^3
Volume = 2.5^3 cm^3 = 15.625 cm^3
density = mass / volume = 42.20 / 15.625 = 2.70 You have 3 places of accuracy.
density of object = 2.70 grams / cm^3 <<<<=== answer.
extinction coefficient (ε) = 347 L·mol⁻¹·cm⁻¹
Explanation:
The chemical reaction between chromium (Cr) and hydrochloric acid (HCl):
2 Cr + 6 HCl → 2 CrCl₃ + 3 H₂
number of moles = mass / molar weight
number of moles of Cr = 0.3 × 10⁻³ (g) / 52 (g/mole)
number of moles of Cr = 5.77 × 10⁻⁶ moles
From the chemical reaction we see that 2 moles of Cr will produce 2 moles of CrCl₃ so 5.77 × 10⁻⁶ moles of Cr will produce 5.77 × 10⁻⁶ moles of CrCl₃.
molar concentration = number of moles / volume (L)
molar concentration of CrCl₃ = 5.77 × 10⁻⁶ / 10 × 10⁻³
molar concentration of CrCl₃ = 5.77 × 10⁻⁴ moles / L
Now we need to transform percent transmittance (%T) in absorbance (A) using the following formula:
A = 2 - log (%T)
A = 2 - log (62.5)
A = 2 - 1.8
A = 0.2
We know that absorbance (A) is defined in respect with extinction coefficient (ε), cell length (l) and concentration (c):
A = εlc
ε = A / lc
ε = 0.2 / (1 × 5.77 × 10⁻⁴)
ε = 0.0347 × 10⁴
ε = 347 L·mol⁻¹·cm⁻¹
Learn more about:
molar concentration
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At constant pressure, temperature is directly proportional to the volume and vise versa. The formula will be
V1/T1 = V2/T2
where V1 and T1 are the initial volume and temperature and V2 and T2 are the final volume and temperature. The temperature is in Kelvin and to convert Celsius to Kelvin add 273.
so, 6.24L/298 = V2/328
=6.87L
In order to determine the number of protons in 20.02 mol of Ne, we use Avogadro's number to convert the number of moles to number of atoms, 1 mol = 6.022 x 10^23 atoms. From there, we must know the number of protons in a Neon atom, which is 10. Thus, the formula will be:
(20.02 mol Ne)x(6.022 x 10^23 atoms/mol)x(10 protons/1 atom Ne) = 1.2056 x 10^26 protons
