Answer:
the color we observe is the wavelength that the object reflects back to us.
Explanation:
light is composed of several wavelengths each wavelengths is a particular color . but for higher wavelengths light becomes invisible. the color we observe is the wavelength of light that the object reflects back to us.
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.
![pOH= -log [2.4 \times 10^-^2] = 1.62\\\\pH = 14 - 1.62= 12.38](https://tex.z-dn.net/?f=pOH%3D%20-log%20%5B2.4%20%5Ctimes%2010%5E-%5E2%5D%20%3D%201.62%5C%5C%5C%5CpH%20%3D%2014%20-%201.62%3D%2012.38)

c. HCl is a strong acid so it dissociates to 0.0001
and 0.0001
, hence
![pH= -log[0.0001] = 4](https://tex.z-dn.net/?f=pH%3D%20-log%5B0.0001%5D%20%3D%204)
![d.pOH= -log [4.4 \times 10^-9] = 8.36\\\\pH= 14- 8.36 = 5.64](https://tex.z-dn.net/?f=%20d.pOH%3D%20-log%20%5B4.4%20%5Ctimes%2010%5E-9%5D%20%3D%208.36%5C%5C%5C%5CpH%3D%2014-%208.36%20%3D%205.64)
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

![K= \frac{[CO_2][SO_2]}{[O_2]}](https://tex.z-dn.net/?f=K%3D%20%5Cfrac%7B%5BCO_2%5D%5BSO_2%5D%7D%7B%5BO_2%5D%7D)
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.
Answer:
Solution's mass = 200.055 g
[PbSO₄] = 275 ppm
Explanation:
Solute mass = 0.055 g of lead(II) sulfate
Solvent mass = 200 g of water
Solution mass = Solvent mass + Solution mass
0.055 g + 200 g = 200.055 g
ppm = μg of solute / g of solution
We convert the mass of solute from g to μg
0.055 g . 1×10⁶ μg/ 1g = 5.5×10⁴μg
5.5×10⁴μg / 200.055 g = 275 ppm
ppm can also be determined as mg of solute / kg of solution
It is important that the relation is 1×10⁻⁶
Let's verify: 0.055 g = 55 mg
200.055 g = 0.200055 kg
55 mg / 0.200055 kg = 275 ppm
Sodium ion is smaller than potassium.
Answer:
1.58x10⁻⁵
2.51x10⁻⁸
0.0126
63.10
Explanation:
Phenolphthalein acts like a weak acid, so in aqueous solution, it has an acid form HIn, and the conjugate base In-, and the pH of it can be calculated by the Handerson-Halsebach equation:
pH = pKa + log[In-]/[HIn]
pKa = -logKa, and Ka is the equilibrium constant of the dissociation of the acid. [X] is the concentrantion of X. Thus,
i) pH = 4.9
4.9 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = - 4.8
[In-]/[HIn] = 
[In-]/[HIn] = 1.58x10⁻⁵
ii) pH = 2.1
2.1 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = -7.6
[In-]/[HIn] = 
[In-]/[HIn] = 2.51x10⁻⁸
iii) pH = 7.8
7.8 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = -1.9
[In-]/[HIn] = 
[In-]/[HIn] = 0.0126
iv) pH = 11.5
11.5 = 9.7 + log[In-]/[HIn]
log[In-]/[HIn] = 1.8
[In-]/[HIn] = 
[In-]/[HIn] = 63.10