If the heating is done on one small area on the top, there will be convection. If the heating is restricted to a small fraction of the heating area, then within that area the heating will go deeper than anywhere else on the surface. Then unheated area will have a shallower region of high temperature. Then some convection will occur in the deeper layers, causing some motion on top.
This happens quite a bit during welding. Convection is very significant in welding, even when the heating is from the top.
1) Chemical equation:
Mg + O2 -> MgO
2) Balanced chemical equation:
2Mg + O2 -> 2MgO
3) Ratios
2 mol Mg : 1 mol O2 : 2 mol MgO
4) Convert 2 grams of Mg to number of moles
Molar mass of Mg: 24.3 g/mol
# of moles = grams / molar mass = 2g / 24.3 g/mol = 0.0823 mol
5) Use the theoretical ratio fo find the number of moles of MgO produced
0.0823 mol Mg * 2mol MgO / 2 mol Mg = 0.0823 mol MgO
6) Use the molar mass of MgO to obtain the quantity in grams
Molar mass of MgO = 24.3 g/mol + 16 g/mol = 40.3 g/mol
0.0823 mol MgO * 40.3 g/ mol = 3.32 g
Answer: 3.32 g
The molar mass is the mass of a given chemical element or chemical compound (g) divided by the amount of substance (mol). The molar mass of a compound can be calculated by adding the standard atomic masses (in g/mol) of the constituent atoms.
Answer:
0.004012km
Explanation:
Problem:
Conversion of millimeters(mm) to Kilometers:
value given = 4012mm
Here, we are converting from a submultiple unit to a multiple unit.
Millimeter depicts 10⁻³m and kilometer stands for 10³m
Now, we must find how many exponents will take us from 10⁻³ to 10³
careful examination shows that if we multiply a power of 10⁶ to 10⁻³ it will give a 10³:
i.e 10⁻³ x 10⁶ = 10⁻³⁺⁶ = 10³
Therefore,
10⁶mm = 1km
4,012mm = = 0.004012km