A
Explanation:
The coiling up of DNA with the help of histone proteins - to what is called heterochromatic regions- is part of gene regulation. This makes genes inaccessible to RNA polymerase that makes mRNA from the genes. When the genes are exposed by DNA unwinding, these genes are transcribed and the resulting mRNAs are translated by ribosomes into proteins.
The DNA never unwinds completely, but rather does so region by region, because if it does so it would become so long that it wouldn't fit in the nucleus or cell.
3.16 X 10^-11 M is the [OH-] concentration when H3O+ = 1.40 *10^-4 M.
Explanation:
data given:
H30+= 1.40 X 10^-4 M\
Henderson Hasslebalch equation to calculate pH=
pH = -log10(H30+)
putting the values in the equation:
pH = -log 10(1.40 X 10^-4 M)
pH = 3.85
pH + pOH =14
pOH = 14 - 3.85
pOH = 10.15
The OH- concentration from the pOH by the equation:
pOH = -log10[OH-]
10.5= -log10[OH-]
[OH-] = 10^-10.5
[OH-] = 3.16 X 10^-11 is the concentration of OH ions when hydronium ion concentration is 1.40 *10^-4 M.
C. Weak acids partially ionize
This is a double replacement reaction; the ions switch twice.
The mass of sodium chloride : 3.5 g
<h3>Further explanation</h3>
Given
Reaction :
2.5g of sodium sulphate + 4.5g of barium chloride ⇒ 3.5g of barium sulphate + sodium chloride
Required
The mass of sodium chloride
Solution
Conservation of mass applies to a closed system, <em>where the masses before and after the reaction are the same</em>
From the reaction :
mass of reactants = 2.5 g + 4.5 g = 7.0 g
mass of products = 3.5 g + mass of sodium chloride
mass of reactants = mass of products
7.0 g = 3.5 g + mass of sodium chloride
mass of sodium chloride = 7 g - 3.5 g =3.5 g
