Which of the following changes are classified as physical changes?
1 answer:
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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.