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:
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Answer:
0.702M
Explanation:
Molarity of a solution, which refers to the molar concentration of that solution can be calculated thus;
Molarity = number of moles (n) ÷ volume (V)
Firstly, we convert 18.5 grams of NaCl to moles using the formula; mole = mass/molar mass
molar mass of NaCl = 23 + 35.5 = 58.5g/mol
mole = 18.5/58.5
mole = 0.32moles
Volume of water (V) = 450mL = 450/1000 = 0.450L
Molarity = n/V
Molarity = 0.32/0.450
Molarity = 0.702M
Answer:
Explanation:
The work function of the lithium = 279.7 KJ/mol (Source)
It means that
1 mole of electrons can be removed by applying of 279.7 kJ of energy.
Also,
1 mole = 
So,
electrons can be removed by applying of 279.7 kJ of energy.
1 electron can be removed by applying of 
of energy.
Energy required = 
Also,
1 kJ = 1000 J
So,
Energy required = 
Also, 
Where,
h is Plank's constant having value 
c is the speed of light having value 
So,
Also,
1 m = 10⁻⁹ nm
So,
Answer:
Molybdenum
Explanation:
Molybdenum is a chemical element with the symbol Mo and an atomic number of 42. This implies a total of 42 electrons in its orbital.
The atomic weight of Mo is 95.94g/mol.
Using the sublevel notation system, the electrons can be filled into the orbitals as shown below:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁴
The ending configuration of this element is therefore 4d⁴
