Question

Calculate the volume of gas produced if 3.0 gram of sodium reacts with excess water at RTP.
​

Answer 1

♠ FOLLOW ♠

♥ Like ♥

♦Hey mate here is your answer♦

♦Calculations involving molar volume - Higher

♦The molar volume can be used in calculations involving the masses of solids, and volumes of gases, in reactions.

♦Calculating a volume from a mass

♦Worked example

4.6 g of sodium reacts completely with excess water:

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

Calculate the volume of hydrogen produced. (Ar of Na = 23, molar volume = 24 dm3)

♦Step 1 - Calculate the amount of sodium

Amount in mol = mass in gAr

Amount in mol = 4.623

Amount of sodium = 0.20 mol

♦Step 2 - Find the amount of hydrogen

From the balanced equation, the mole ratio Na:H2 is 2:1

Therefore 0.20 mol of Na produces 0.202 = 0.10 mol of H2

♦Step 3 - Calculate the volume of hydrogen

Volume = amount in mol × molar volume

Volume = 0.10 × 24

= 2.4 dm3.........

♦Calculating a mass from a volume

♦Worked example

♦Lithium hydroxide absorbs carbon dioxide from the air:

2LiOH(s) + CO2(g) → Li2CO3(s) + H2O(l)

♦Calculate the mass of lithium hydroxide needed to absorb 12 dm3 of carbon dioxide. (Mr of LiOH = 24, molar volume = 24 dm3)

♦Step 1 - Calculate the amount of carbon dioxide

Amount in mol = volumemolar volume

Amount in mol = 1224

= 0.50 mol

♦Step 2 - Find the amount of lithium hydroxide

From the balanced equation, the mole ratio LiOH:CO2 is 2:1

Therefore 0.50 mol of CO2 is absorbed by (0.50 × 2) = 1.0 mol of LiOH

♦Step 3 - Calculate the mass of lithium hydroxide

Mass in g = Mr × amount in mol

Mass = 24 × 1.0

[= 24 g] .....Is your answer....