Question

Acetylene gas $ \left( {{C_2}{H_2}} \right) $ is produced as a result of the reaction $ Ca{C_{2\left( s \right)}} + 2{H_2}{O_{\left( l \right)}} \to {C_2}{H_{2\left( g \right)}} + Ca{\left( {OH} \right)_{2\left( {aq} \right)}} $ . If $ 10g $ of $ Ca{C_2} $ are consumed in this reaction, how much $ {H_2}O $ is needed? Answer in units one mol.

Answer 1

Hint: Given that when calcium carbide and water are reacted leads to the formation of acetylene and calcium hydroxide. Given is the amount of calcium carbide consumed in the reaction. Molar mass of calcium carbide is $ 64gmo{l^{ - 1}} $ Thus, the number of moles of calcium carbide will be obtained. From the balanced chemical equation, the number of moles of water needed will be calculated from the number of moles of calcium carbide.

Complete Step By Step Answer:
Acetylene gas is an unsaturated hydrocarbon with the molecular formula of $ {C_2}{H_2} $
The given chemical reaction is $ Ca{C_{2\left( s \right)}} + 2{H_2}{O_{\left( l \right)}} \to {C_2}{H_{2\left( g \right)}} + Ca{\left( {OH} \right)_{2\left( {aq} \right)}} $
Given the mass of calcium carbide consumed in the reaction is $ 10g $
The molar mass of calcium carbide is $ 40 + 2\left( {12} \right) = 64gmo{l^{ - 1}} $
The number of moles will be calculated by dividing the mass of calcium carbide with molar mass of calcium carbide which is $ \dfrac{{10}}{{64}} = 0.156mol $
The number of moles of calcium carbide consumed in the reaction is $ 0.156mol $
For every one mole of calcium carbide, two moles of water were reacted. Thus, the number of moles of water needed in the given reaction is $ 2 \times 0.156 = 0.312mol $
The amount of water $ \left( {{H_2}O} \right) $ needed in the reaction is $ 0.312mol $ .

Note:
While calculating the number of moles the amount of substance must be in grams and the molar mass should be exactly calculated from the molar mass of all the atoms in the substance. Some atoms may not have molar mass equal to the double of the atomic number.