Why do we use the HCl moles to calculate the mass of MgCl2 in the reaction of Mg and HCl? Chemical formula; Ammonium chloride Iron 3 sulfate Magnesium phosphate Chemical name; Cs2CO3 K2Cr2O3?

In the reaction of Mg and HCl, we use the moles of HCl to calculate the mass of MgCl2 because the balanced chemical equation for the reaction shows a 1:1 mole ratio between HCl and MgCl2. This means that for every mole of HCl that reacts, one mole of MgCl2 is produced. By knowing the moles of HCl used in the reaction, we can determine the moles of MgCl2 produced and then calculate the mass of MgCl2 based on its molar mass.

As for the chemical formulas and names you provided:
- Ammonium chloride: NH4Cl
- Iron (III) sulfate: Fe2(SO4)3
- Magnesium phosphate: Mg3(PO4)2
- Cesium carbonate: Cs2CO3
- Potassium chromate: K2CrO4

In the reaction between Mg and HCl, we use the moles of HCl to calculate the mass of MgCl2 because the stoichiometry of the reaction tells us that 2 moles of HCl react with 1 mole of Mg to produce 1 mole of MgCl2.

Balanced chemical equation:

```
Mg + 2HCl → MgCl2 + H2
```

From the balanced equation, we can see that:

- 1 mole of Mg reacts with 2 moles of HCl
- 1 mole of Mg produces 1 mole of MgCl2

Therefore, to calculate the mass of MgCl2 produced, we need to know the moles of HCl that reacted. Once we know the moles of HCl, we can use the mole ratio from the balanced equation to determine the moles of MgCl2 produced. Finally, we can use the molar mass of MgCl2 to convert moles to mass.

Example:

Suppose we have 0.1 moles of HCl. Using the stoichiometry of the reaction, we can calculate the moles of MgCl2 produced as follows:

```
0.1 moles HCl × (1 mole MgCl2 / 2 moles HCl) = 0.05 moles MgCl2
```

Finally, we can convert moles to mass using the molar mass of MgCl2 (95.21 g/mol):

```
0.05 moles MgCl2 × 95.21 g/mol = 4.76 g MgCl2
```

Therefore, the reaction of 0.1 moles of HCl with Mg will produce 4.76 g of MgCl2.

Chemical formulas and names:

- Ammonium chloride: NH4Cl
- Iron 3 sulfate: Fe2(SO4)3
- Magnesium phosphate: Mg3(PO4)2
- Cs2CO3: Cesium carbonate
- K2Cr2O3: Potassium dichromate