Question

4. Calcium reacts with water as shown.
Ca(s) + 2H2O(l) = Ca(OH)2(aq) + H2(g)
what is the total mass of the solution that remains when 40 g of calcium reacts with 100 g of water​

Answer 1

Answer:

140g

Explanation

in any chemical equation mass is always conserved so even after reacting and changing the total mass still stays the same which to begin was 100 + 40 which is 140. so the answer is 140g remains

Answer 2

Given :

Calcium reacts with water according to the equation:

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

To Find:

The total mass of solution left when 40 g Calcium reacts with 100 g of water

Solution:

• As per the equation Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g),

      1 mole of calcium reacts with 2 moles of water to produce 1 mole of calcium hydroxide.

1. Mass of 1 mole of calcium = 40 g
2. Mass of 1 mole of water = 18 g
3. Mass of 1 mole of calcium hydroxide = 74 g

• According to the question,

      Mass of calcium given = 40 g = 1 mole

      Mass of water given = 100 g = $\frac{100}{18}$ moles

• If 2 moles of H₂O reacts with 1 mole of Ca, then

                       $\frac{100}{18}$ moles of H₂O will react with

                      ⇒ $\frac{1}{2}$ × $\frac{100}{18}$ = 2.77 moles of Ca

• Since, only 1 mole of Ca is given, therefore it is the limiting reagent. Products will be decided based on the limiting reagent.

• So, when 1 mole of Ca reacts with water,

1. Mass of water left unreacted = 100-18= 82 g
2. Mass of calcium hydroxide produced = 74 g

Therefore, 82 g of water remains and 74 g of calcium hydroxide is formed when 40 g of calcium reacts with 100 g of water.