Answer
a. FM of C$H_{3}$OH = 32.0 amu.
b. FM N$O_{3}$ = 62.0 amu
c. FM $K_{2}CO_{3}$ = 138.2 amu
d. FM of $Ni_{3}(PO_{4})_{2}$ = 366 amu
Work Step by Step
a. Formula mass for methanol C$H_{3}$OH.
FM of C$H_{3}$OH is the sum of atomic masses of all atoms in formula:
1 x AM of C = 1 x 12.01 amu = 12.01 amu
4 x AM of H= 4 x 1.00 amu = 4.00 amu
1 x AM of O = 1 x 15.99 amu = 15.99 amu
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FM of C$H_{3}$OH = 12.01 amu + 4.00 amu + 15.99 amu
FM of C$H_{3}$OH = 32.00 amu
FM of C$H_{3}$OH = 32.0 amu.
b. Formula mass for nitrogen trioxide N$O_{3}$ .
FM of N$O_{3}$ is the sum of atomic masses of all atoms in formula:
1 x AM of N = 1 x 14.00amu = 14.00 amu
3 x AM of O = 3 x 15.99 amu = 47.97 amu
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FM N$O_{3}$ = 14.00 amu + 47.97 amu
FM N$O_{3}$ = 61.97 amu
FM N$O_{3}$ = 62.0 amu
c. Formula mass for potassium carbonate $K_{2}CO_{3}$ .
FM of $K_{2}CO_{3}$ is the sum of atomic masses of all atoms in formula:
2 x AM K = 2 x 39.09 amu= 78.18 amu
1 x AM C = 1 x 12.01 amu = 12.01 amu
3 X AM O = 3 x 15.99 amu = 47.97 amu
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FM $K_{2}CO_{3}$ = 78.18 amu + 12.01 amu + 47.97 amu
FM $K_{2}CO_{3}$ = 138.16 amu
FM $K_{2}CO_{3}$ = 138.2 amu
d. Formula mass for nickel (II) phosphate $Ni_{3}(PO_{4})_{2}$ .
FM of $Ni_{3}(PO_{4})_{2}$ is the sum of atomic masses of all atoms in formula:
3 x AM of Ni = 3 x 58.69 amu = 176.07 amu
2 x AM of P = 2 x 30.97 amu = 61.94 amu
8 x AM of O = 8 x 15.99 amu = 127.92 amu ______________________________________
FM of $Ni_{3}(PO_{4})_{2}$ = 176.07 amu + 61.94 amu + 127.92 amu
FM of $Ni_{3}(PO_{4})_{2}$ = 365.93 amu
FM of $Ni_{3}(PO_{4})_{2}$ = 366 amu
