The number of moles of HCl in an aqueous hydrochloric acid solution can be determined as follows moles=(concentration in M units) (Volume in liters)
for example - in 10.00 ml of 10 M HCI, the number of moles is: moles = (10 moles/L) (0.0100 L) = 0.10 moles
Using this method, which of the follow is correct for the Zn+HCl reaction? we were asked to mix 2 g of Zn with 10ml of HCL
1) HCl reagent was added in excess
2) HCl was the limiting reagent
3) Zn and HCl were added in the stoichiometric amounts
4) The reaction stoichiometry of Zn and HCl cannot be determined

1) HCl reagent was added in excess

Explanation:

The equation of the reaction is given as;

Zn + HCl --> ZnCl2 + H2

From the stoichiometry;

1 mol of Zn reacts with 1 mol of HCl

In 2g of Zn;

mass = 2

Molar mass = 65.38g/mol

Number of moles = Mass/ Molar mass = 2 / 65.38 = 0.03059 mol

In 10ml of HCl;

the number of moles is: moles = Concentration * Volume =  (10 moles/L) (0.0100 L) = 0.10 moles

Comparing 0.03059 mol  of Zn : 0.10 mol of HC with the stochiometry, we can deduce that HCl is by far greater. Hence the correct option is option 1.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.