Chemistry Homework Help

Chemistry
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Jun 5th, 2015

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DATA:

Number of atoms= 7.5*1015

Mass in grmas=?

SOLUTION:

6.02*1023 atoms are present in 1 mol of Ni

7.5*1015 atoms are present in (1*7.5*1015)/6.02*1023

  = 1.2458*10-8 mol

Mole of Ni = mass of Ni in grmas/ atomic mass of Ni

Mass of Ni= mole of Ni * atomic mass of Ni

Mass of Ni = 1.2458*10-8 * 58.6934

Mass of Ni = 7.3123*10-7g

DATA:

Mass of aspirin= 0.1g

Number of molecules = ?

SOLUTION:

Mole of aspirin = mass of aspirin/ molecular mass of aspirin

  = 0.1 /180

  = 5.5555*10-4

1 mol aspirin contains 6.02*1023 molecules

5.5555*10-4 contains (6.02*1023* 5.5555*10-4)

  =3.3444*1020 molecules


Please let me know if you need any clarification. I'm always happy to answer your questions.
Jun 5th, 2015

i am getting back to you with the solution of other three in a while. hope you'll understand

Jun 5th, 2015

DATA:

Percentage of Ag= 63.5%

Percentage of N=  8.25%

Percentage of O2 = 100-63.5-8.25= 28.25%

Empirical formula=?

SOLUTION

STEP 1:

DETERMINE MOLES

Mol of Ag = 63.5/107.86 = 0.5887mol

Mole of N = 8.25/14.00 = 0.5892mol

Mole of O2 = 28.25/15.99 = 1.7667mol

STEP 2:

DTERMINE RATIOS

Ag= 0.5887/0.5887 = 1

N= 0.5892/0.5887 = 1.000

O2 = 1.7667/0.5887 = 3.00

STEP 3:

WRITW EMPIRICAL FORMULA

AgNO3

DATA:

Molecular mass = 42g/mol

Empirical formula = CH2

Molecular formula =?

SOLUTION:

STEP 1:

DETERMINE ā€˜nā€™

n = molecular mass/empirical formula mass

n= 42/14

n= 3

STEP 2

DTERMINE MOLECULAR FORMULA

Molecular formula = (empirical formula)n

Molecular formula = (CH2)3

Molecular formula = C3H6

DATA:

Mass of sample= 60g

Percentage of Pb = 64%

Percentage of C = 29.7%

Percentage of H = 6.2%

Empirical formula=?

SOLUTION:

STEP 1

DETERMINE MASS OF ELEMENTS IN THE GIVEN MASS OF SAMPLE

Mass of Pb= (64*60)/100 = 38.4g

Mass of C= (29.7*60)/100 = 17.82g

Mass of H = (6.2*60)/100 = 3.72g

STEP 2

DETERMINE MOLES

Moles of Pb = 38.4/207.2 = 0.1853mol

Moles of C = 17.82/12.01= 1.4837mol

Moles of H= 3.72/1.00 = 3.72mol

STEP 3

DETERMINE RATIOS

Pb= 0.1853/0.1853 = 1

C= 1.4837/0.1853= 8.00

H= 3.72/0.1853= 20.07

STEP 4

WRITE EMPIRICAL FORMULA
C8H20Pb


Jun 5th, 2015

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