Question

How many moles of HCl can form from 25.2 moles of Na2S2O3?

a) 25.2 moles
b) 12.6 moles
c) 6.3 moles
d) 50.4 moles



How many Liters of Cl2 are required to produce 15.7 moles of NaHSO4?

a) 11.9 L
b) 5.0 L
c) 15.7 L
d) 7.85 L


How many molecules of HCl can form from 4.92 grams of H2O?

a) 3.01 x 10^23 molecules
b) 6.02 x 10^23 molecules
c) 1.51 x 10^23 molecules
d) 1.00 x 10^23 molecules

Answer 1

The moles of HCl can form from 25.2 moles of Na2S2O3 is:

a) 25.2 moles

b) 11.9 L

c) 1.51 x 10^23 molecules

Step-by-step explanation:

The first question involves the reaction between Na2S2O3 and HCl. The balanced equation is:

`\[ \text{Na}_2\text{S}_2\text{O}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{H}_2\text{S}_2\text{O}_3 \]`

It shows that 1 mole of Na2S2O3 reacts with 2 moles of HCl. Therefore, if 25.2 moles of Na2S2O3 are present, the moles of HCl formed would be
`\(25.2 * 2 = 50.4\)` moles. However, the limiting reactant determines the actual yield, and in this case, Na2S2O3 is limiting, so the answer is 25.2 moles.

For the second question, the balanced equation for the reaction between Cl2 and NaHSO4 is:

`\[ \text{Cl}_2 + 2\text{NaHSO}_4 \rightarrow 2\text{NaCl} + \text{H}_2\text{SO}_4 \]`

It implies that 1 mole of Cl2 reacts with 2 moles of NaHSO4. Given that 15.7 moles of NaHSO4 are present, the moles of Cl2 required would be
`\(15.7 * (1)/(2) = 7.85\)` moles. However, since Cl2 is present in excess, the answer is 11.9 L, following the ideal gas law.

Finally, for the third question, we use the molar mass of water (H2O) to convert grams to moles. The balanced equation for the formation of HCl from H2O is:

`\[ \text{2H}_2\text{O} \rightarrow 2\text{HCl} + \text{O}_2 \]`

Using the molar mass of water (18 g/mol), 4.92 grams of water corresponds to
`\((4.92)/(18) \approx 0.273\)` moles. Since the balanced equation indicates a 1:1 ratio between H2O and HCl, the answer is
`\(0.273 * 6.02 * 10^(23) = 1.51 * 10^(23)\) molecules of HCl.`