The us environmental protection agency (epa) places limits on the quantities of toxic substances that may be discharged into the sewer system. limits have been established for a variety of substances including hexavalent chromium which is limited to 0.50 mg/l .if an industry is discharging hexavalent chromium as potassium dichromate (k2cr2o7), what is the maximum permissible molarity of that substance?

4.8x10⁻⁶ M

Explanation:

The question asks for the maximum molarity of K₂Cr₂O₇ that can be discharge into the sewer system if the limit of hexavalent chromium (Cr(VI)) that is permmitted to discharge is 0.50 mg/L.

Molarity is defined as moles of K₂Cr₂O₇ per Liter, so we need to calculate to how many moles of K₂Cr₂O₇ corresponds the 0.50 mg of Cr(VI).

In 1 mol of K₂Cr₂O₇ there are 2 moles of Cr(VI) which are 103.99 g of Cr(VI) (2 * molar mass of Cr = 2 * 51.9961 g/mol)

So 103.99 g of Cr(VI) can be found in 1 mol of K₂Cr₂O₇

We need to calculate in how many moles of K₂Cr₂O₇ we can find 0.50 mg or 5.0x10⁻⁴ g of Cr(VI) (1 g = 1000 mg) :

x moles K₂Cr₂O₇ / 5.0x10⁻⁴ g Cr(VI) = 1 mol K₂Cr₂O₇ / 103.99 g Cr(VI)

x = 5.0x10⁻⁴ g * (1 mol K₂Cr₂O₇ / 103.99 g Cr(VI)) = 4.8x10⁻⁶ moles K₂Cr₂O₇

4.8x10⁻⁶ moles K₂Cr₂O₇ can be discharged per Liter

So the maximum permissible molarity of K₂Cr₂O₇ is 4.8x10⁻⁶ M

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

answer; the numbers of valence electrons in the acetic acid molecule (ch3co2h) is 24;