Okay
40ml-35ml=5ml
5ml is the volume of the rock
1ml=1cm3
hence the volume of the rock is 5cm3
Answer:
B They move because of the convection currents in the mantle.
Answer:


Explanation:
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In this case, since the reaction (A->B) have an initial amount of pure 4-aminobenzoic acid, the first step to compute the theoretical yield is to solve the following stoichiometric setup:

Whereas A stands for 4-aminobenzoic acid and B for the benzocaine. Moreover, we compute the percent yield by dividing the actual yield (0.318 g) by the theoretical one (0.365 g):

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Answer:
HF is the limiting reactant
Explanation:
The balanced equation for the reaction is given below:
SiO₂ + 4HF —> SiF₄ + 2H₂O
From the balanced equation above,
1 mole of SiO₂ reacted with 4 moles of HF.
Finally, we shall determine the limiting reactant. This can be obtained as illustrated below:
From the balanced equation above,
1 mole of SiO₂ reacted with 4 moles of HF.
Therefore, 7.5 moles of SiO₂ will react with = 7.5 × 4 = 30 moles of HF.
From the calculation made above, we can see clearly that it will take a higher amount (i.e 30 moles) of HF than what was given from the question (i.e 5 moles) to react completely with 7.5 moles of SiO₂.
Therefore, HF is the limiting reactant and SiO₂ is the excess reactant.