<u>Answer:</u> The volume of stock solution of strontium hydroxide needed is 4.125 mL
<u>Explanation:</u>
1 mole of 
produces 1 mole of strontium ions and 2 moles of hydroxide ions
Molarity of diluted strontium hydroxide solution = 
To calculate the molarity of the diluted solution, we use the equation:
where,
are the molarity and volume of the concentrated strontium hydroxide solution
are the molarity and volume of diluted strontium hydroxide solution
We are given:
Putting values in above equation, we get:
Hence, the volume of stock solution of strontium hydroxide needed is 4.125 mL
Answer:
A. Iodine
Explanation:
First 2 points describe it's physical properties. Even if we don't remember them, we can easily figure out the answer to be a non-metal. As, non-metals usually have lower bp and mp than metals.
Both Iodine and hydrogen exists as a 2 atom molecule in gas phase.
But only elements of group 17 (halogens) have 7 electrons in their outer shell.
Again, salts are usually ionic compounds, formed by atoms with a greater difference in their electronegativities. Hence, the one that forms bonds with a metal to form a salt readily can be a non- metal.
All these points indicate that the element must be iodine.
Answer:
Approximately 4574.86 years
Explanation:
Hello,
To find the age of this sample, we should first of all convert the disintegration per minute to per year so that we can work on the same unit as our half life (T½), then we can find the disintegration constant and use it to find the year of the artifact.
Data;
T½ = 5730 years
Initial rate of radioactivity (No) = 15.3 disintegration per minute.
Current rate of radioactivity (N) = 8.8 disintegration per minute.
1 year = 525600 minutes
1 mins = 8.8 disintegration
525600mins = N disintegration
N = (525600 × 8.8) / 1
N = 4625280
1 mins = 15.3 disintegration
525600 mins = No
No = 8041680
But T½ = In2 / λ
λ = In2 / T½
λ = 0.693 / 5730
λ = 1.209×10⁻⁴ (this is the disintegration constant)
We can now find the how old the artifact is using our disintegration constant and other parameters.
In(N÷No) = -λt
In[4625280 / 8041680] = -(1.209×10⁻⁴ × t)
In[0.57516] = -1.209×10⁻⁴t
-0.5531 = -1.209×10⁻⁴ t
Solve for t
t = 0.5531 / 1.209×10⁻⁴
t = 4574.86 years
The artifact is approximately 4574.86 years
Answer:
see explanation!
Explanation:
1a. There are no gaps/sticks between the potassium ions and sulfide ions.
1c. (two) shared pairs between H and S 1
(rest correct - no additional hydrogen electrons and two non-bonding pairs on sulfur second mark dependent on first)
1d. (2 × 27) + 3[32 + (16 × 4)] = 342
The answer is: K is more reactive than Ca because K has to lose only one electron to complete its outermost shell.
Potassium is a chemical element with atomic number 19 (number of electrons is 19).
Electron configuration of potassium is: ₁₉K 1s²2s²2p⁶3s²3p⁶4s¹.
Potassium is the alkali metal and has a single valence electron in the outer electron shell.
Periodic law is the arrangement of the elements in order of increasing atomic number.
For example all alkaline metals (I group of periodic table, Na, K, Cs...) loose one electron in chemical reaction and react vigorously with water.
Reactivity series is an empirical progression of a series of metals, arranged by their reactivity from highest to lowest (alkaline metals have highest reactivity and Noble metals lowest reactivity).
The ionization energy (Ei) is the minimum amount of energy required to remove the valence electron, when element lose electrons, oxidation number of element grows (oxidation process).
Alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons (one electron, earth alkaline metals (right next to alkaline metals) have higher ionization energy than alkaline metals, because they have two valence electrons.
