A gas that has a volume of 28 liters, a temperature of 45 °C, and an unknown pressure has its volume increased

to 34 liters and its temperature decreased to 35 °C. If I measure the pressure after the change to be 2.0 atm,

what was the original pressure of the gas?

2.5 atm

Explanation:

V1 = 28L

T1 = 45°C = (45 + 273.15)K = 318.15K

V2 = 34L

T2 = 35°C = (35 + 273.15)K = 308.15k

P2 = 2.0atm

P1 = ?

From general gas equation,

(P1 × V1) / T1 = (P2 × V2) / T2

P2 × V2 × T1 = P1 × V1 × T2

P1 = (P2 × V2 × T1) / (V1 × T2)

P1 = (2.0 × 34 × 318.15) / (28 × 308.15)

P1 = 21634.5 / 8628.2

P1 = 2.5 atm

The initial pressure of the gas is 2.5atm

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:

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.