Answer:
When there remains one-quarter of the sample, the age of the sample is 10940 years
Explanation:
<u>Step 1:</u> Data given
The half-life of C-14 is 5470 years.
The half- life time is the time required for a quantity to reduce to half of its initial value.
This means after 5470 years there remains half of the C-14 sample.
To remain a quarter of the sample, another cycle of 5470 years is required.
This means 2 half-lives should have passed to remain a quarter of the sample.
<u>Step 2</u>: Calculate it's age
t/(t/1/2) = 2
⇒ with t = the age (or time) of the sample
⇒ with t(1/2) = the half-life time of the sample = 5470 years
⇒ with 2 = the number of halvf- lives passed
t/5470 = 2
t = 2*5470 = 10940 years
When there remains one-quarter of the sample, the age of the sample is 10940 years
Answer:
A. Molarity will increase .
Explanation:
Molarity = moles of solute per litre of solution
= moles of solute / volume of solution
If evaporation occurs , volume of solution decreases and moles of solute remains constant . Hence denominator decreases and numerator remains constant .
Hence the molarity increases .
Answer: The mass is 980.6g of Gold.
Explanation:
We begin by looking for the number of moles equivalent to 3.0 x 10^24 gold atoms.
Using the Avogadro's number,
6.02 x 10^23 atoms of gold make up 1 mole of gold.
3.0 x 10^24 atoms would make up: 1 / 6.02 x 10^23 x 3.0 x 10^24 = 4.98moles.
Now that we know the number of moles, we can then look for the mass using the formular:
Moles = mass/ molar mass
4.98 = mass / 196.9 (atomic mass of gold)
Making "mass" the subject of formula : mass = 4.98 x 196.9= 980.6g
In the reaction 2co ( g) + o2( g) → 2co2( g), the ratio of moles of oxygen used to moles of co2produced is 1:2.
Answer:
Option B is correct. A nuclear alpha decay
Explanation:
Step 1
This equation is a nuclear reaction. So it can be an alpha decay or a beta decay
An α-particle is a helium nucleus. It contains 2 protons and 2 neutrons, for a mass number of 4.
During α-decay, an atomic nucleus emits an alpha particle. It transforms (or decays) into an atom with an atomic number 2 less and a mass number 4 less.
Thus, radium-226 decays through α-particle emission to form radon-222 according to the equation that is showed.
A Beta decay occurs when, in a nucleus with too many protons or too many neutrons, one of the protons or neutrons is transformed into the other.
Option B is correct. A nuclear alpha decay
