I\'ve done these probelms incorrectly. Please show me how to solve them correctl

Question

I've done these probelms incorrectly. Please show me how to solve them correctly.

1.The molecular weight of anhydrous calcium chloride is 110.99 grams/mol. How many grams do you need for 750 ml of 250uM calcium chloride?

250 E-6 = x/110.99(1000/750)

250 E-6 = 4x/110(3)

= 0.0189g/ml

2. You have 12 mL of cells you need to treat with Hydrogen Peroxide (H2O2), such that the final concentration of H2O2 is 50 uM. How much of a 30 mM stock solution of H2O2 would you add to your cells?

N1V1=N2V2

50uM(12mL)=30mM(1000)

600= 30,000N2

N2 =0.02mM

She cricled mM on this one, so I

Explanation / Answer

Hi,

A) Since, The molecular weight of anhydrous calcium chloride is 110.99 grams/mol

110.99 g/mol of anhydrous calcium chloride in 1000mL water gives you 1M solution

which means, 83.2425 g/mol (=110.99*750/1000) of anhydrous calcium chloride in 750mL water would give you 1M solution

Now, 20.811 g/mol (=83.2425*0.25/1) of anhydrous calcium chloride in 750mL water would give you 0.25 M solution

Therefore, 0.0208 g (20.811 X 10-3 g) of of anhydrous calcium chloride in 750mL water would give you 0.25mM ( 250uM) solution

B)

Given : N1 = 30 mM

V1=?

N2= 50

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