AP chem question!!!! Please help ?

Question

35

(a) what is the mass, in grams, of 2.50 x 10^-3 mol of ammonium phosphate?

(b) How many moles of chloride ions are in 0.2550 g of aluminum chloride?

(c) what is the mass, in grams, of 7.70 x 10^20 molecules of caffeine, C_8H_10N_4O_2?

(d) What is the mole mass of cholesterol if 0.00105 mol weighs 0.406?

Please show all work and explain if u want

I have listed this question several times to get in noticed so please just answer one of them

thanks for ur help and yes i tried on my own first and got some where but i know its all wrong.

Answer 1

a) what is the mass, in grams, of 2.50 x 10^-3 mol of ammonium phosphate, using its molar mass of 149.12g/mol:

2.50 e-3 mol  @ 149.12g/mol = 0.3728 grams

your answer is(3 sig figs): 0.373 grams (NH4)3PO4

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(b) How many moles of chloride ions are in 0.2550 g of aluminum chloride using AlCl3 's molar mass of 133.34 g / mol:

0.2550 g AlCl3 @ 3 moles Cl- / 133.34 grams AlCl3 = 0.0057372 moles

your answer is(4 sigfigs): 0.005737 moles Cl-

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(c) what is the mass, in grams, of 7.70 x 10^20 molecules of caffeine, C_8H_10N_4O2  using the molar mass of caffeine of 194.19 g/mol:

7.70 e20 molecules @ 194.19 grams / 6.022e23 molecules = 0.2483 grams

Your answer (3 sigfigs): 0.248 g of caffeine

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(d) What is the mole mass of cholesterol if 0.00105 mol weighs 0.406 grams?

0.406 grams / 0.00105 moles = 386.66666

your answer is (3 sigfigs): 387 g / mole is the molar mass of cholesterol