Answer:
a) the atomic number is 15
b) the mass number is 15+16 = 31
c) element is phosphorus
d)Group 15 period 3
Answer:
So first thing to do in these types of problems is write out your chemical reaction and balance it:
Mg + O2 --> MgO
Then you need to start thinking about moles of Magnesium for moles of Magnesium Oxide. Based on the above equation 1 mole of Magnesium is needed to make one mole of Magnesium Oxide.
To get moles of magnesium you need to take the grams you started with (.418) and convert to moles by dividing by molecular weight of Mg (24.305), this gives you .0172 moles of Mg.
The theoretical yield would be the assumption that 100% of the magnesium will be converted into Magnesium Oxide, so you would get, based on the first equation, .0172 mol of MgO. Multiplying this by the molecular weight of MgO (24.305+16) gives us .693 g of MgO.
The percent yield is what you actually got in the experiment, and for this you subtract off the total mass from the crucible mass, or 27.374 - 26.687, which gives .66 g of MgO obtained.
Percent yield is acutal/theoretical, .66/.693, or 95.24%.
I'll let you do the same for the second trial, and average percent yield is just an average of the two trials percent yield.
Hope this helps.
Answer:
The sample of lead has a volume of 11.1 cm³
Explanation:
<u>Step 1:</u> Data given
x cm³ lead has a density of 11.3 g/cm³
it has the same mass as 330cm³ of a piece of redwood with density 0.38g/cm³
<u>Step 2</u>: Calculate mass of the piece of redwood
Density = mass/volume
mass = density * volume
Mass of the piece of redwood = 0.38 g/cm³ * 330cm³ = 125.4 grams
Since the sample of lead has the same mass, it also has a mass of 125.4 grams
<u>Step 3</u>: Calculate volume of the lead
Density = mass/ volume
Volume = mass/ density
Volume of lead = 125.4g / 11.3g/cm³ = 11.097 cm³≈11.1 cm³
The sample of lead has a volume of 11.1 cm³
Explanation:
this is a process were by water vapour goes up to the atmosphere and cool which makes cloud's. then water vapour begins to accumulate and when the clouds are heavy then they pour down rain etc
