There are 3 beakers each of which contains saline solution.
beaker a initially contains 3 liters of 10\% salt solution.
beaker b initially contains 2 liters of 20\% salt solution.
beaker c initially contains 4 liters of 0\% salt solution.

two liters are transferred from a to b and the result is thoroughly mixed. then one liter is transferred from b to c and the result mixed. finally two liters are transferred from c back to a. what is the percentage concetration of salt in a after all this?

percentage concentration of salt in a= \%

Percentage concentration of salt in A = 5.3%

Explanation:

Assume all the concentrations are expressed in volumetric terms, i.e 10% = 10 liter salt / 100 liter solution, 20% = 20 liter salt / 100 liter soluton, 0% = 0 liters salt.

1) First transformation: 2 liters are from A to B

Solution A:

Concentration: 10 % salt ⇒ 10 liter salt / 100 liter solutionVolume of solution: 3 litersVolume of salt: 3 liters × 10 liter / 100 liters = 0.300 liter saltVolume of water: 3 liters - 0.300 liters = 2.700 liters solvent

Solution B:

Concentraion: 20%Volume of solution: 2 literVolume of salt: 2 liter × 0.20 = 0.4 liter saltVolume of water: 2 liter - 0.4  liter = 1.6 liter water

Resultant mixture in beaker B: 2 liters of solution A plus 2 liters of solution B

Salt: 2 liter × 0.10 + 2 liter × 0.20 = 0.20 + 0.4 = 0.6 liter salt

                             

Water: 2 liter × 0.90 + 2 liter × 0.80 = 3.40 liter waterSolution: 2 liter + 2 liter = 4 liter solutionConcentration: 0.6 liter salt / 4 liter solution = 0.15 = 15%

2) Second transformation: 1 liter transferred from B to C

Salt: 1 liter × 0.15 + 0 = 0.15 liter salt

                       ↑              ↑

                  (from B)     ( in C)

Solution: 1 liter + 4 liter = 5 liter solutionConcentration: 0.15 liter salt / 5 liter solution = 0.03 = 3.0%

3) Third transformation: 2 liters are from C to A.

Salt: 0.03 liter salt × 2 liter solution + 1 liter × 0.10 = 0.16 liter salt

                                       ↑                                    ↑

                                (from C)                             (in A)

Solution: 2 liter + 1 liter = 3 liter solution% of salt in A = (0.16 liter salt / 3 liter solution) × 100 =5.3 %

The molecules contain like 54 of water 

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer