Explanation:
In a double displacement reaction, there is an actual exchange of partners to form new compounds.
The reaction is given as shown below:
AB + CD → AD + CB
One of the following conditions serves as the driving force for a double replacement reaction:
- Formation of an insoluble compound or precipitate
- Formation of water or any other non-ionizing compound
- Liberation of a gaseous product.
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Answer:
1) 0.3g Mg
2)0.5g MgO
3)0.2g O
4)0.01mol Mg & 0.01mol O
5)0.01mol MgO
6) Empirical formula MgO
Explanation:
The mass og Mg is obtained by substracting 24.36g from 24.66g:
24.66 - 24.36 = 0.3g Mg
The ignition of Mg means that it's reacting with oxygen to form an oxide. The increase in the crucible mass after the Mg ignition is due to the addition of oxygen. However, the addition of few drops of water produces a new compound: a hydroxide. According to the oxidation state og Mg (2+), the only magnesium oxide possible is MgO. It happens because the oxidation state of oxygen in oxides is 2-. Which means that just one oxygen atom is required to electrically neutralize one magnesium atom.
We can use a conversion factor to know how much MgO is made from from 0.3 g of Mg:
*
= 0.2g O
Thereby the mass of the oxide is 0.2g O + 0.3g Mg = 0.5g MgO
We convert the mass of oxygen and magnesium to the respective amounts in moles by using conversion factors:
*
= 0.01mol O
*
= 0.01mol Mg
The moles of MgO can be obtained from:
*
= 0.01mol MgO
To obtain the empirical formula, the amount fo moles of each elements must be divided by the smallest one, in this case, 0.01.
The result for both number of Mg atoms and O atoms is 1. This can be interpreted to mean that there is a Mg atom for each O atom forming the formula unit of the compound.
The step when water is added to the compound resulting after heating does not affect the calculations necessary for the magnesium oxide.
Answer:
D) 65.7%
Explanation:
Based on the reaction:
2H2(g)+O2(g)⟶2H2O(l)
<em>2 moles of hydrogen produce 2 moles of water assuming an excess of oxygen.</em>
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To find percent yield of the reaction we need to find theoretical yield (The yield assuming all hydrogen reacts producing water). With theoretical yield and actual yield (32.8g H₂O) we can determine percent yield as 100 times the ratio between actual yield and theoretical yield.
<em>Theoretical yield:</em>
Moles of 5.58g H₂:
5.58g H₂ ₓ (1 mol / 2.016g) = 2.768 moles H₂
As 2 moles of H₂ produce 2 moles of H₂O, if all hydrogen reacts will produce 2.768 moles H₂O. In grams:
2.768 moles H₂O ₓ (18.015g / mol) =
49.86g H₂O is theoretical yield
<em>Percent yield:</em>
Percent yield = Actual yield / Theoretical yield ₓ 100
32.8g H₂O / 49.86g ₓ 100 =
65.7% is percent yield of the reaction
<h3>D) 65.7%
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