Answer:
14.68 moles of He
Explanation:
To do this, just remember Avogadro's Constant or Avogadro's number. This constant tells us how many units ( in this case atoms) there are in a mole of ANY type of substance.
Avogadro's constant is 6.022140857 × 10²³ units per mole.
Now that we know how many atoms there are in 1 mole, we can use this as our conversion factor.
8.84 x 10²⁴ atoms of He → moles of He

So the answer would be:
14.68 moles of He
Answer:
2KBr + MgF₂ –> 2KF + MgBr₂
The coefficients are: 2, 1, 2, 1
Explanation:
KBr + MgF₂ –> KF + MgBr₂
The above equation can be balance as illustrated below:
KBr + MgF₂ –> KF + MgBr₂
There are 2 atoms of F on the left side and 1 atom on the right. It can be balance by writing 2 before KF as shown below:
KBr + MgF₂ –> 2KF + MgBr₂
There 2 atoms of K on the right side and 1 atom on the left side. It can be balance by writing 2 before KBr as shown below:
2KBr + MgF₂ –> 2KF + MgBr₂
Now, the equation is balanced.
The coefficients are: 2, 1, 2, 1