Question

al₂(so₄)₃
express your answer in atomic mass units to two decimal places.
formula mass =
amu
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part d
(nh₄)₂cr₂o₇
express your answer in atomic mass units to two decimal places.
formula mass =
amu

Explanation:

Step1: Identify atomic masses

Atomic mass of Al = 26.98 amu, S = 32.07 amu, O = 16.00 amu, N = 14.01 amu, H = 1.01 amu, Cr = 52.00 amu.

Step2: Calculate formula - mass of $Al_2(SO_4)_3$

For $Al_2(SO_4)_3$, there are 2 Al atoms, 3 S atoms and 12 O atoms.
Formula - mass = \(2\times26.98+3\times32.07 + 12\times16.00\)
\[

$$\begin{align*} &=53.96+96.21+192.00\\ &=342.17\text{ amu} \end{align*}$$

\]

Step3: Calculate formula - mass of $(NH_4)_2Cr_2O_7$

For $(NH_4)_2Cr_2O_7$, there are 2 N atoms, 8 H atoms, 2 Cr atoms and 7 O atoms.
Formula - mass=\(2\times14.01 + 8\times1.01+2\times52.00+7\times16.00\)
\[

$$\begin{align*} &=28.02+8.08 + 104.00+112.00\\ &=252.10\text{ amu} \end{align*}$$

\]

Answer:

For $Al_2(SO_4)_3$, formula - mass = 342.17 amu
For $(NH_4)_2Cr_2O_7$, formula - mass = 252.10 amu