Answer:
Explanation:
The usefulness of a buffer is its ability to resist changes in pH when small quantities of base or acid are added to it. This ability is the consequence of having both the conjugate base and the weak acid present in solution which will consume the added base or acid.
This capacity is lost if the ratio of the concentration of conjugate base to the concentration of weak acid differ by an order of magnitude. Since buffers having ratios differing by more will have their pH driven by either the weak acid or its conjugate base .
From the Henderson-Hasselbach equation we have that
pH = pKa + log [A⁻]/[HA]
thus
0.1 ≤ [A⁻]/[HA] ≤ 10
Therefore the log of this range is -1 to 1, and the pH will have a useful range of within +/- 1 the pKa of the buffer.
Now we are equipped to answer our question:
pH range = 3.9 +/- 1 = 2.9 through 4.9
Sorry for the delay! My internet is a bit bad.
P is the third sublevel. Each sublevel (the angular momentum quantum number), has its own number:
<span>s = 1, p =3, d = 5, f = 7</span>
The number of electrons for each is:
s-2
p-6
d-10
f-14
It's easier to just memorize these numbers, but the equation for determining the sublevel number is 2n (n = the principal quantum number). The principal quantum number is based on the period the element is in.
It has 7.22 moles.... mole =mass/molar mass
molar mass of H2O=18
130/18=mole
The number of joules released when 0.64g of steam are cooled from 125 c to 105 c is -26.112 joules
calculation
by use of Q=MCΔ T formula calculate the joules released where
Q( heat) =?
M (mass) = 0.64 g
C (specific heat capacity = 2.04 j/g/c
ΔT(change in temperature) = 105-125 =-20c
Q is therefore = 0.64 g x2.04 j/g/c x -20 c = -26.112 joules
it is okay to have negative value since the reaction is exothermic that is heat is released
