Answer:
<h3>The answer is 78 g</h3>
Explanation:
The mass of a substance when given the density and volume can be found by using the formula
<h3>mass = Density × volume</h3>
From the question
volume = 10 cc
density = 7.8 g/cc
So we have
mass = 7.8 × 10
We have the final answer as
<h3>78 g</h3>
Hope this helps you
Answer:

Explanation:
Hello!
In this case, since the combustion reaction of methanol is:

In such a way, since there is 1:3/2 mole ratio between methanol and oxygen, we can compute the moles of oxygen that are needed to burn 2.56 moles of methanol as shown below:

Best regards!
Answer:
the unknown substance is a protein
Explanation:
The biuret test is one of the tests for proteins. It can be used to detect peptide linkages. The biuret test is carried out in an alkaline solution. A coordination complex is formed leading to the appearance of a violet color.
Summarily, the biuret method is a colorimetric technique used to test for proteins and peptides. It involves the formation of a purple (violet) complex of Copper salts in alkaline solution.
Hence when the biuret reagent is added to an unknown substance and it turns purple, the unknown substance is a protein
There's 6.022×10^23 particles in 1 mole of anything
like there is 1000 grams in 1 kilogram of anything
30 because it is the highest number of marriage