2.56 grams of zinc react with excess phosphoric acid to produce how many molecules of hydrogen gas?

Zn + 2HCl ==> ZnCl2 + H2

mols Zn = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols Zn to mols H2.
Then mols H2 gas x 6.02E23 molecules/mol H2 = ? # molecules H2 gas.

To determine the number of molecules of hydrogen gas produced when 2.56 grams of zinc react with excess phosphoric acid, you will need to follow these steps:

1. Write a balanced chemical equation for the reaction between zinc and phosphoric acid. In this case, the balanced equation is:

3Zn + 2H3PO4 -> 3Zn(H2PO4)2 + 3H2

This equation shows that three molecules of zinc react with two molecules of phosphoric acid to produce three molecules of zinc dihydrogen phosphate and three molecules of hydrogen gas.

2. Calculate the moles of zinc in 2.56 grams using its molar mass. The molar mass of zinc (Zn) is approximately 65.38 g/mol. Therefore, the number of moles of zinc can be calculated as:

Number of moles = Mass of substance (in grams) / Molar mass

Number of moles of zinc = 2.56 g / 65.38 g/mol = 0.0391 mol (rounded to four decimal places)

3. Identify the stoichiometric ratio between zinc and hydrogen gas from the balanced equation. The stoichiometric ratio indicates the number of molecules of hydrogen gas produced for each molecule of zinc that reacts. In this case, the stoichiometric ratio is 3:3 (same numbers).

4. Calculate the number of moles of hydrogen gas produced using the stoichiometric ratio. Since the stoichiometric ratio is 3:3, the number of moles of hydrogen gas produced will be the same as the number of moles of zinc:

Number of moles of hydrogen gas = 0.0391 mol

5. Convert the number of moles of hydrogen gas into molecules. In one mole of any substance, there are 6.022 x 10^23 particles (Avogadro's number). Therefore, the number of molecules can be calculated by multiplying the number of moles by Avogadro's number:

Number of molecules = Number of moles x Avogadro's number

Number of molecules of hydrogen gas = 0.0391 mol x 6.022 x 10^23 molecules/mol = 2.353 x 10^22 molecules

Therefore, when 2.56 grams of zinc reacts with excess phosphoric acid, it produces approximately 2.353 x 10^22 molecules of hydrogen gas.