Most buffers are a mixture of a weak acid and its conjugate base. buffers resist changes in ph when small amounts of acid or base are added. the effective ph range of a buffer depends on the pka of the acid and the relative concentrations of the acid, ha, and its conjugate base, a−. the equation for the acid dissociation of a weak acid is: ha(aq) + h2o(l) ⇌ a−(aq) + h3o+(aq) the equation for the acid dissociation constant is: ka equals concentration of h3o+ times concentration of a− divided by concentration of ha rearrange the equation and then substitute in pka = −log(ka) and ph = −log(h3o+): ph equals pka plus log of the result of the concentration of a− divided by concentration of ha this expression is the henderson-hasselbalch equation and is useful for determining the ph of a buffer solution. a buffer solution has 0.620 m hf and 0.710 m f−. if 0.025 moles of hcl is added to 325 ml of the buffer solution, what is the ph after the addition? the pka of hydrofluoric acid is 3.16.

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation:

answer

fusion: the energy source of stars. the energy released from the collapse of the gas into a protostar causes the center of the protostar to become extremely hot. when the core is hot enough, nuclear fusion commences. fusion is the process where two hydrogen atoms combine to form a helium atom, releasing energy.

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1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

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