Answer:
A. 4.
Explanation:
<em>no. of moles (n) = mass/molar mass.</em>
mass = 64.0 g, molar mass = 16.0 g/mol.
∴ no. of moles (n) = mass/molar mass = (64.0 g)/(16.0 g/mol) = 4 mol.
Answer:
1. negative
2. positive
3. neutral
Explanation:
Ok so it looks like they are asking for the charge (positive, negative, or neutral) of each thing
So for 1, it would be negative, because it's pointing to an electron. Electrons always have a negative charge.
So for 2, it would be positive, because it's pointing to a proton. Protons always have a positive charge
So for 3, it would be neutral, because it's pointing to a neutron. Neutrons always have a neutral charge.
Answer:
a) a0 was 46.2 grams
b) It will take 259 years
c) The fossil is 1845 years old
Explanation:
<em>An unknown radioactive substance has a half-life of 3.20hours . If 46.2g of the substance is currently present, what mass A0 was present 8.00 hours ago?</em>
A = A0 * (1/2)^(t/h)
⇒ with A = the final amount = 46.2 grams
⇒ A0 = the original amount
⇒ t = time = 8 hours
⇒ h = half-life time = 3.2 hours
46.2 = Ao*(1/2)^(8/3.2)
Ao = 261.35 grams
<em>Americium-241 is used in some smoke detectors. It is an alpha emitter with a half-life of 432 years. How long will it take in years for 34.0% of an Am-241 sample to decay?</em>
t = (ln(0.66))-0.693) * 432 = 259 years
It will take 259 years
<em>A fossil was analyzed and determined to have a carbon-14 level that is 80% that of living organisms. The half-life of C-14 is 5730 years. How old is the fossil?</em>
<em />
t = (ln(0.80))-0.693) * 5730 = 1845
The fossil is 1845 years old
A. Zn²⁺
<h3>Further explanation</h3>
Given
Cations of several elements
Required
The least to be reduced
Solution
If we look at the voltaic series:
<em>Li-K-Ba-Ca-Na-Mg-Al-Mn- (H2O) -Zn-Cr-Fe²⁺-Cd-Co-Ni-Sn-Pb- (H) -Cu-Hg-Fe³⁺-Ag-Pt-Au </em>
The electrode which is easier to reduce than the hydrogen (H2) electrode has a positive sign (E red= +) and is located to the right of the voltaic series (right of H)
The electrode which is easier to oxidize than the hydrogen (H2) electrode and is difficult to experience reduction has a negative sign (E red= -) and is located to the left of the voltaic series (left of H)
Or you can look at the standard reduction potential value of the metals in the answer options, and the most negative reduction E° value which will be difficult to reduce.
The Zn metal is located far left of the other metals in the answer choices, so it is the most difficult to reduce