Identify the following atom
1 answer:
You might be interested in
Answer:
Explanation:
The half-life of Na-24 (15 h) is the time it takes for half of it to decay.
After one half-life, half (50 %) of the original amount will remain.
After a second half-life, half of that amount (25 %) will remain, and so on.
We can construct a table as follows:
No. of Fraction Mass
<u>half-lives t/da Remaining Remaining/g </u>
0 0 1 18
1 15 ½ 9.0
2 30 ¼ 4.5
3 45 ⅛ 2.2
4 60 ⅟₁₆ 1.1
5 75 ⅟₃₂ 0.56
6 90 ⅟₆₄ 0.28
We see that remain after five half-lives (75 h).
Question 1
The correct answer is a.
Explanation
The relationship between and
is given by
, We can use
and
. In a we are given the concentration of [OH] and so we use that to find the pOH, then from pOH we can find the pH.
c. HCl is a strong acid so it dissociates to 0.0001 and 0.0001
, hence
has a pH 12.36 which is greater than 7
Question 2
The correct answer is d .
Explanation
This is because solids and liquids do not appear in the equilibrium constant expression. Since .
For the equation
Question 3
The correct answer is c
In a molecule the oxidation number are assigned to get the sum of a neutral charge or ion. The overall charge of is -2 and in all its compounds oxygen has -2 charge, hence
Question 4
The correct answer is b. An oxidising agent must gain electrons in a reaction, thus it is the one that undergoes reduction.In order find out what is being reduced we write half reactions for molecules that change their state. and
are spectactor ions in this reaction.
In the chloride half reaction gains electrons to become
ions.
Question 5
The last element D is correct. When a nucleus decays by beta emission it produces a daughter nucleus that has same mass number but different atomic number. Therefore beta-decay will have equation
Question 6
The correct answer is a. A beta particle is an electron because it has a charge of -1 and has same mass as an electron, while a positron is a particle with the same mass as an electron but with a positive charge.
We must first find the molar weight of Tungsten, found on the periodic table as 183.84g per mole.
We are told to find the mass of a sample containing 0.700 moles of Tungsten, so we can set this up in a multiplication equation and cancel units to find the mass in grams:
So the answer that is closest to this value is C) 129g.
We are told to find the mass of a sample containing 0.700 moles of Tungsten, so we can set this up in a multiplication equation and cancel units to find the mass in grams:
So the answer that is closest to this value is C) 129g.