Answer:
10.
Step-by-step explanation:
Hello,
In this case, for the given reaction:
![Cr + Fe(NO_3)_2 \rightarrow Fe + Cr(NO_3)_3](https://img.qammunity.org/2021/formulas/chemistry/college/t17vbaia3fu2jeg0f7v8nli50oyow9jbbn.png)
By knowing the law of conservation of mass must be respected, the following coefficients do balance the chemical equation:
![2Cr + 3Fe(NO_3)_2 \rightarrow 3Fe + 2Cr(NO_3)_3](https://img.qammunity.org/2021/formulas/chemistry/college/mnm3b6uyi1hanwgsvzna0id14mdcxeh4i7.png)
So the sum of all the coefficients is 10.
Regards.