For each of these equations determine the change in the number of moles of gas δngas.

Of each of these equations, determine the change in the number of moles (change in n gas)


(a) (NH4)2CO3(s) yields 2NH3 (g) + CO2 (g) + H2O (g) ___________ mol

(b) H2 (g) + Cl2 (g) yields @HCl (g) ___________ mol

(c) 2H2 (g) + O2 (g) yields 2H2O (l) ___________ mol

(d) 2Na (s) + Cl2 (g) yields 2NaCl (s) ___________ mol


Answer

General guidance

Concepts and reason

A mole represents the amount of chemical substances present in the system. In a balanced chemical equation, number of atoms on the reactant side will be equal to number of atoms on the product. Based on the balanced chemical equation, the amount of species that have participated in the chemical reaction and the amount of product formed can be determined.

Fundamentals

For a balanced chemical equation, Numbers of atoms in reactant side = Numbers of atoms in product side Mass of the substance
Number of moles =
Molar mass of the substance An, = n(products)- n(reactants)
An, Change in number of moles of gas
n(products) = Sum of number of moles of products in gas

Step-by-step

Step 1 of 4

(a) The given reaction was written as follows, (NH,), CO, (s)
+2NH,(g)+CO,(g)+H2O(g) The number of atoms on the reactant side is equal to the number of atoms on the product side, therefore the given reaction is balanced. In the above reaction one mole of reactant in the solid state produces four mole of gaseous product Δη, = 2+1+1-0
= 4 mol

Part a

The change in the moles of gas is 4mol.


The given equation is in balanced form. The number of atoms in reactant side is equal to number of atoms in the product side. In the above reaction one mole of reactant in the solid state produces four mole of gaseous product. There is no reactant in the gaseous state, all of the products are gases, therefore from the equation it was identified that change in the moles of gas is

Step 2 of 4

(b) Write the given reaction, H2(g)+Cl2(g)
→ HCl(g) Balance the above reaction: H, (g)+Cl2(g)
→ 2HCl(g) An = 2-1-1
= 0 mol

Part b

The change in the moles of gas is Omol.


The given equation is unbalanced, coefficient two was added before the product to attain the balanced equation. The by applying the coefficient in the formula, the change in the number moles of gas was identified as zero.

Step 3 of 4

(c) The given reaction, 2H, (g)+O2(g)
2H20 (1) The given reaction is in balanced form An, = 0-2-1
= -3mol In the above reaction two moles of hydrogen in gas state react with one mole of oxygen in gas state to produce two moles of water in liquid form. Change in number of moles of gas during the reaction was calculated as .

Part c

The change in the moles of gas is -3mol.


In given equation is in balanced form. Two moles of hydrogen in gas state react with one mole of oxygen in gas state to produce two moles of water in liquid form. Change in number of moles of gas during the reaction was calculated as .

Step 4 of 4

(d) The given reaction is 2Na(s)+Cl(g)—2NaCl(s) The given reaction is in balanced form An = 0-1
= -1 mol In the above reaction two moles of sodium in solid state react with one mole of chlorine in gas state to produce two moles of sodium chloride in solid state. Change in number of moles of gas during the reaction was calculated as.

Part d

The change in the moles of gas is - 1 mol.


Balanced form of the reaction was given. In the given reaction two moles of sodium in solid state react with one mole of chlorine in gas state to produce two moles of sodium chloride in solid state. Change in number of moles of gas during the reaction was calculated as.

Answer

Part a

The change in the moles of gas is 4mol.

Part b

The change in the moles of gas is Omol.

Part c

The change in the moles of gas is -3mol.

Part d

The change in the moles of gas is - 1 mol.


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