Letter d, because they are both alkali metals (group one)
MgCl₂)= Mg²⁺ + 2Cl⁻
V(MgCl₂)=285cm³=0,285dm³
c(MgCl₂)=0,015 mol/dm³
n(MgCl₂)=c·V= 0,015 mol/dm³ · 0,285dm³ = 0,0042 mol
n(Mg²⁺)=n(MgCl₂)=0,0042 mol
n(Cl⁻)=2n(MgCl₂)=0,0084 mol
The answer: is yes, It is a buffer solution.
first, we need to get moles of sodium hydroxide and propanoic acid:
moles NaOH = molarity * volume
= 0.5M * 0.1 L = 0.05 moles
moles propanoic acid = molarity * volume
= 0.75 M * 0.1 L = 0.075 moles
[NaOH] at equilibrium = 0.05 m
[propanoic acid ] at equilibrium = 0.075 - 0.05 = 0.025 m
when Pka for propanoic acid (given) = 4.89
so by substitution:
∴PH = Pka + ㏒[NaOH]/[propanoic acid ]
∴ PH = 4.89 + ㏒ 0.05 / 0.025
= 5.19
We assume that this gas is an ideal gas. We use the ideal gas equation to calculate the amount of the gas in moles. It is expressed as:
PV = nRT
(672) (1/760) (36.52) = n (0.08206) ( 68 +273.15)
n = 1.15 mol of gas
Hope this answers the question. Have a nice day.