Answer:
Na₂CO₃.2H₂O
Explanation:
For the hydrated compound, let us denote is by Na₂CO₃.xH₂O
The unknown is the value of x which is the amount of water of crystallisation.
Given values:
Starting mass of hydrate i.e Na₂CO₃.xH₂O = 4.31g
Mass after heating (Na₂CO₃) = 3.22g
Mass of the water of crystallisation = (4.31-3.22)g = 1.09g
To determine the integer x, we find the number of moles of the anhydrous Na₂CO₃ and that of the water of crystallisation:
Number of moles = 
Molar mass of Na₂CO₃ =[(23x2) + 12 + (16x3)] = 106gmol⁻¹
Molar mass of H₂O = [(1x2) + (16)] = 18gmol⁻¹
Number of moles of Na₂CO₃ = 
= 0.03mole
Number of moles of H₂O = 
= 0.06mole
From the obtained number of moles:
Na₂CO₃ H₂O
0.03 0.06
Simplest
Ratio 0.03/0.03 0.03/0.06
1 2
Therefore, x = 2
Answer: a. The concentrations of the reactants and products have reached constant values
Explanation:
The reactions which do not go on completion and in which the reactant forms product and the products goes back to the reactants simultaneously are known as equilibrium reactions. For a chemical equilibrium reaction, equilibrium state is achieved when the rate of forward reaction becomes equal to rate of the backward reaction.
Equilibrium state is the state when reactants and products are present but the concentrations does not change with time and are constant.
Equilibrium constant is defined as the ratio of concentration of products to the concentration of reactants each raised to the power their stoichiometric ratios. It is expressed as 
K is the constant of a certain reaction when it is in equilibrium, while Q is the quotient of activities of products and reactants at any stage other than equilibrium of a reaction.
For a equilibrium reaction,
![K_{eq}=\frac{[B]}{[A]}](https://tex.z-dn.net/?f=K_%7Beq%7D%3D%5Cfrac%7B%5BB%5D%7D%7B%5BA%5D%7D)
Thus the correct answer is the concentrations of the reactants and products have reached constant values.
Answer:
7.5 g of hydrogen gas reacts with 50.0 g oxygen gas to form 57.5 g of water.
Explanation:
Here we have the check if the mass of the reactants is equal to the mass of the products.
Reactants
Products
The data is consistent with the law of conservation of matter.
Reactants
Products
The data is not consistent with the law of conservation of matter.
Reactant
Products
The data is not consistent with the law of conservation of matter.
Only the first data is consistent with the law of conservation of matter.
The number of moles in 3.20 x 10² formula units of calcium iodide is 0.053 moles.
<h3>How to calculate number of moles?</h3>
The number of moles in the formula units of a substance is calculated by dividing the formula unit by Avogadro's number.
According to this question, 3.20 x 10² formula units are in calcium iodide. The number of moles is as follows:
no of moles = 3.20 x 10²² ÷ 6.02 × 10²³
no of moles = 0.53 × 10-¹
no of moles = 0.053 moles
Therefore, the number of moles in 3.20 x 10² formula units of calcium iodide is 0.053 moles.
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