Remember this:
atomic mass= atomic number + number of neutrons
The atomic number (same thing as number of protons) in this case is 15. The atomic mass is 31.
So, we subtract 15 from 31 to find the number of neutrons.
31-15=16
16 neutrons!!!
Answer:
MgSo4 : 7H2O
Mr 120 : Mr 126
mass 80: x
then cross multiply
Explanation:
making x the subject of the formula then you will get 84 as the mass of water
Be careful on this one! Mass is always conserved, based on the law of conservation of mass. Since their was a change in state, we went from a solid to a gas, so, the weight would be lighter, not the mass.
Same amount of mass.
Avagadro's number is just a measurement. One mole is 6.022 X 10^23 of anything - atoms, molecules, marbles... anything.
<span>1) If one mole = 6.022 X 10^23, then 8.00mol of H2S is: </span>
<span>(3.00mol H2S) (6.022 X 10^23 molecules H2S / 1 mol H2S) = 1.8060 X 10^24 molecules H2S. </span>
<span>Rounded to 3 sig figs =1.81 X 10^24 molecules H2S
</span>part2.
<span> This one uses moles in the stoichiometric sense as well as the measurement. One formula unit of MgCl2 contains 1 mole Mg and 2 moles Cl. </span>
<span>First, figure out how many moles of formula units there are. </span>
(1.81 X 10^24 FU's) (1mol MgCl2 / 6.022 X 10^23 FU's) = 3.0056mol MgCl2.
<span>Now, we know that there are 2 moles of Cl in every mole of MgCl2 (2 Cl atoms in every unit of MgCl2). From this we can determine how many moles of Cl atoms there are: </span>
<span>(3.0056mol MgCl2) (2mol Cl atoms / 1mol MgCl2) = 6.0112mol Cl atoms. </span>
<span>Now round to 3 sig figs = 10.0mol Cl atoms</span>
