Answer:
Specific Heat Capacity = 0.901 J.g⁻¹.°C⁻¹
Heat is Exothermic
Explanation:
Specific heat capacity is the amount of heat required to raise the temperature of a given amount of substance by one degree.
Also, Exothermic reactions are those reaction in which the heat is lost from the system to surrounding while, endothermic reactions are those in which the system gains heat from the surroundings.
The equation used for this problem is as follow,
Q = m Cp ΔT ----- (1)
Where;
Q = Heat = 14200 J
m = mass = 350 g
Cp = Specific Heat Capacity = ??
ΔT = Change in Temperature = 70 °C - 25 °C = 45 °C
Solving eq. 1 for Cp,
Cp = Q / m ΔT
Putting values,
Cp = 14200 J / (350 g × 45 °C)
Cp = 0.901 J.g⁻¹.°C⁻¹
As the heat is lost by the metal therefore, the heat is exothermic.
Answer:
6.574 g NaF into 300ml (0.25M HF) => Bfr with pH ~3.5
Explanation:
For buffer solution to have a pH-value of 3.5 the hydronium ion concentration [H⁺] must be 3.16 x 10⁻⁴M ( => [H⁺] = 10^-pH = 10⁻³°⁵ =3.16 x 10⁻⁴M).
Addition of NaF to 300ml of 0.25M HF gives a buffer solution. To determine mass of NaF needed use common ion analysis for HF/NaF and calculate molarity of NaF, then moles in 300ml the x formula wt => mass needed for 3.5 pH.
HF ⇄ H⁺ + F⁻; Ka = 6.6 x 10⁻⁴
Ka = [H⁺][F⁻]/[HF] = 6.6 x 10⁻⁴ = (3.16 x 10⁻⁴)[F⁻]/0.25 => [F⁻] = (6.6 x 10⁻⁴)(0.25)/(3.16x10⁻⁴) = 5.218M in F⁻ needed ( = NaF needed).
For the 300ml buffer solution, moles of NaF needed = Molarity x Volume(L)
= (5.218M)(0.300L) = 0.157 mole NaF needed x 42 g/mole = 6.574 g NaF needed.
Check using the Henderson - Hasselbalch Equation...
pH = pKa + log ([Base]/[Acid]); pKa (HF) = 3.18
Molarity of NaF = (6.572g/42g/mole)/(0.300 L soln) = 0.572M in NaF = 0.572M in F⁻.
pH = 3.18 + log ([0.572]/[0.25]) ≅ 3.5.
One can also back calculate through the Henderson -Hasselbalch Equation to determine base concentration, moles NaF then grams NaF.
It is A. This is because, according to your diagram, the sunlight hits the moon, and it is blocking some of the sunlight to reach the Earth. This means that it is in between both of them.
Answer:
Should be 0.6106 though i could be wrong
Explanation:
