<span>Answer:
The half-reaction is as followed:
Cr2O72â’(aq) + 14H+ + 6e⒠→ 2Cr3+(aq) + 7H2O
From the half-reaction, you can retrieve the following information:
1 mole of potassium dichromate =6 moles of e^-
6 moles of e^-=2 moles of Cr
You will also need the following information:
1 mole of e^-=96,485 C
and
1 mole of Cr=52.00g
Calculate the number of moles that 4.94mg equates too:
4.94 mg=4.94 x 10^-3g of chromium*(1 mol/52.00g)=9.50 x 10^-5 mole of Cr
How many moles of electrons are need to produce 9.50 x 10^-5 mole of Cr? Solve for moles of electrons:
9.50 x 10^-5 mole of Cr*(6 moles of e^-/2 mole of Cr)=2.85 x 10^-4 moles of e^-
Whats the charge of 2.85 x 10^-4 moles of electrons? Use Faraday's constant:
2.85 x 10^-4 moles of e^-*(96,485 C/1 mole of e^-)=2.750 x 10^1 C
Since current (A)=charge (C)/time (s), solve for time:
A=C/s
C/A=s
2.750 x 10^1 C/0.234 A=time (s)
1.18 x 10^2 s=118s=time <= 3 significant figures</span>
We calculate it as follows:
Moles CO2 = 0.01849 g / 44 = 0.000420
<span>Mass C = 0.000420 x 12 = 0.00504 g </span>
<span>Moles H = 2 x 0.006232 / 18 = 0.000692 </span>
<span>Mass H = 0.000692 g </span>
<span>Mass O = 0.005982 - ( 0.00504 + 0.000692) = 0.00025 </span>
<span>Moles O = 0.00025 / 16 = 0.0000156 </span>
<span>C 0.000420
H 0.000692
O 0.0000156
</span>
<span>divide each by the smallest value, giving you the chemical formula as:
</span><span>
C27H44O</span>
Answer:
Since different isotopes of an element have different numbers of neutrons (but always the same number of protons) they have different mass numbers. Nitrogen-14 and nitrogen-15 are both stable isotopes of nitrogen. However, the other 5 isotopes are all unstable.
Answer:
Cobaltous Nitride,I think so anyway.......
