An unknown element was collected during a chemical reaction. The sample of the unknown element with a mass of 4.00 g was then allowed to react with excess oxygen, forming an oxide with a mass of 6.63 g. The oxide contains an equal amount (in mol) of both elements.
Identify the unknown element.
Answers
Answer: Magnesium
Explanation: Since the oxide contains an equal amount in mol of both elements, the formula of the oxide can be deduced as XO, where X is the unknown element.
Using the information in the question, you can write a balanced chemical equation for the formation of the oxide:
\(\qquad\qquad\text{2X + O}_2 → \text{2XO}\)
If 6.63 g of the oxide was formed using 4.00 g of the unknown element, the mass of oxygen can then be calculated using the Law of Conservation of Mass.
\(\qquad\qquad \text{6.63 g XO – 4.00 g X = 2.63 g O}\)
You can now use the mass of oxygen to determine the amount in mol of oxygen:
\(\qquad\qquad\dfrac{2.63\text{ g O}}{16.00\text{ g mol}^{−1}} = \text{0.164 mol O}\)
Since the unknown element reacted with oxygen in a 1 : 1 mol ratio, this is also equal to the amount in mol of the unknown element, 0.164 mol X.
Using the mass of the unknown element and the amount in mol calculated above, the molar mass can be calculated:
\(\qquad\qquad\dfrac{\text{4.00 g X}}{\text{0.164 mol X}} = 24.39\text{ g mol}^{−1}\)
The element with a molar mass closest to this value is magnesium.
The unknown element is magnesium.
Given,
The mass of the unknown element is = 4.00 g
The mass of the oxide is = 6.63 g
To find,
To Identify the unknown element.
Solution,
As the oxide contains an equal number in mol, the formula of the oxide can be written as XO, where X is the unknown element.
The balance chemical formula is written as:
2X + O₂ →2XO
Now, using the law of conservation of mass,
∴ 6.63 g XO – 4.00 g X = 2.63 g O
Also, using the mass of oxygen to determine the amount in mol of oxygen:
∴ 2.63g O ×16.00 g mol^−1 = 0.164 mol O
Also, the unknown element reacts with oxide in a 1 : 1 mol ratio which is to the amount in mol is 0.164 mol X.
Again, the molar mass can be calculated:
∴ 4.00 g X×0.164 mol X = 24.39g mol^−1
Hence, the element with a molar mass is magnesium.
#SPJ3