Ask Me Help Desk - Solutions calculations explain

Quote:

11. Calculate the mass of sodium hypochlorite required to prepare 375mL of a bathroom cleaner that contains 1.50% w/v (g/ml) sodium hypochlorite.

12. What mass of ethanol is in a 330 mL can of low alcohol beer that contains 3.80% v/v ethanol? The density of ethanol is 0.785g mL.

13.a in a fully charged car battery, the concentration of sulfuric acid is 445g L.

a. if the volume of acid in the battery is 3.80L, what amount, in mole, of sulfuric acid is present?

15. Calculate the mass of ammonia, Nh3, in 25mL of a 0.0185 mol L ammonia solution.

m=0.0815mol x 7= 0.315g

11. 1.5% w/v = 1.5g / 100 mL

$\frac {1.5g}{100mL} = \frac {x}{375mL}$

$MW\,of\,H_2SO_4= 98 \, \frac {g}{/mol}$

It doesn't matter what the substance is.

12.

$330mL \,\times\,0.038 = Volume\, of\, ethanol$

$volume (in \, mL) \,\times\, 0.785 \frac {g}{mL} \,= \,grams\,of\,ethanol$

13. $[H_2SO_4]=445 \,\frac gL$ (I don't think this is the correct density. I think it's closer to 1800 g/L, but I'll use what was given ).

a. if the volume of acid in the battery is 3.80L, what amount, in mole, of sulfuric acid is present?

$3.08L \,\times\, 445 \,\frac gL \,=\,weight\,of\,H_2SO_4\,in\,g$

$MW\,of\,H_2SO_4=98.08 \,\frac {g}{mole}$

$g \,\div\, \frac {g}{mole} = mole$

15
$25\,mL\,\times\,0.0185\,\frac {moles}{L}\,\times\,0.001\,\frac {L}{mL} = X\,moles$

You now have the number of moles, The molecular weight is in grams per mole (g/mole). So, what do you need to do with the molecular weight to get grams? Multiply or Divide?

In #15, notice how the units cancel. Most of this problem sheet can be solved simply by noting the units of various parameters, and figuring out how to multiply them or divide them so that the unrequired units cancel.