Lithium metal decomposes in water and releases hydrogen gas. if 275 ml of hydrogen gas is produced at stp. what is the mass of lithium that reacted ? Li(s)+H2O(l)=LiOH(aq)+H2(g)
Convert 275 mL H2 gas at STP to mols.
275/22,400 = ??
Use the coefficients to convert mols H2 to mols Li.
Then g Li = mols Li x atomic mass Li.
0.171 g Li
To find the mass of lithium that reacted in the given chemical reaction, we need to use the stoichiometry of the balanced equation. The balanced equation for the reaction is:
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
According to the balanced equation, it takes 2 moles of lithium (Li) to produce 1 mole of hydrogen gas (H2). We also know that 1 mole of any gas at STP (Standard Temperature and Pressure) occupies a volume of 22.4 liters.
Given that 275 mL of hydrogen gas is produced at STP, we need to convert this volume to moles using the ideal gas law equation:
PV = nRT
Where:
P = Pressure (STP = 1 atm)
V = Volume (275 mL = 0.275 L)
n = Moles of the gas (To be determined)
R = Ideal gas constant (0.0821 L⋅atm/mol⋅K)
T = Temperature in Kelvin (STP = 273 K)
Rearranging the equation, we get:
n = PV / RT
n = (1 atm) × (0.275 L) / (0.0821 L⋅atm/mol⋅K) × (273 K)
By calculating the value of 'n', we will find the number of moles of hydrogen gas produced.
After determining the number of moles of H2, we can use the stoichiometry of the balanced equation to relate it to the moles of lithium (Li). Since the ratio of Li to H2 is 2:1, the number of moles of Li will be half of the moles of H2.
Finally, using the molar mass of lithium (6.94 g/mol), we can convert the moles of Li to grams.
Let's perform the calculations:
Step 1: Calculate the number of moles of H2
n = (1 atm) × (0.275 L) / (0.0821 L⋅atm/mol⋅K) × (273 K)
n ≈ 0.0105 mol (rounded to four decimal places)
Step 2: Calculate the number of moles of Li
Moles of Li = 0.0105 mol / 2
Moles of Li = 0.00525 mol
Step 3: Calculate the mass of Li
Mass of Li = Moles of Li × Molar mass of Li
Mass of Li = 0.00525 mol × 6.94 g/mol
Mass of Li ≈ 0.036 g (rounded to three decimal places)
Therefore, the mass of lithium that reacted is approximately 0.036 grams.