It depends on the compound.
The correct statements are:
<span>Hardness is a physical property
</span><span>Friedrich Mohs developed the standard hardness scale.
Diamond can scratch quartz.</span>
For each compound, i.e. galena, cerussite and anglesite calculate the quantity of Pb contained.
For that, you need to use the molecular formula and the atomic weights of the elements.
Galena, PbS
Atomic weights
Pb: 207 uma
S: 32 uma
Molar mass = 207 + 32 = 239 g/mol
Proportion of Pb in the compound = 207/239
% of Pb from galena: 38.0% * [207/239]
Cerussite
Pb CO3
Atomic weights
Pb: 207
C: 12
O: 16
Molar mass = 207 + 12 + 3*16 = 267 g/mol
% of Pb coming from the cerussite
25.0% * [207/267]
Anglesite, PbSO4
Molar mass: 207 + 32 + 4*16 = 303 g/mol
% of Pb coming from anglesite = 17.4% * [207/303]
Total quantity of Pb from the rock (call X the quantity of rock)
[38.0%*207/239 + 25.0%*207/267 + 17.4%*207/303]*X.
And that must be equal to 5.8 metric tons = 5800 kg
The result of the calculations are:
[32.91% + 19.38% + 11.89%]X = 5800 KG
64.18% X = 5800 KG
0.6418 X = 5800 KG
X = 5800 / 0.6418
X = 9037 KG
Which you have to express with two significan figures, i.e. 9000 kg
Answer:
C: The shape of the pebbles is a result of weathering and deposition
Explanation:
For the several pebbles to have a rounded shape and smooth to the touch, it will undergo weathering and deposition. This is because weathering involves breaking down of rocks and creating new sediments. This weathering could be either chemical weathering or physical weathering where Chemical weathering is the decomposition of rocks which are caused by chemical reactions and which result in formation of new compound while physical weathering is the breakdown of rocks into smaller pieces. On the other hand, deposition occurs when the agents of erosion such as wind or water deposit sediments from one spot to another which in turn changes the shape of the land.
Thus, the shape of the pebbles are as a result weathering of the parent rocks and from deposition.