solution:
You need to find the frequency, and they have already given you the wavelength. And since you already know the speed of light, you can use formula (2) to answer this problem. Remember to convert the nano meters to meters because the speed of light is in meters. 

D it’s quartz on the Mohs scale thing it’s ranked 7
A condensation reaction is described to be a reaction wherein two molecules form an even larger product and consequently produces a smaller molecule as a by-product. For example, when two amino acids are combined, a dipeptide bond is formed. As a result, 1 molecule of water is produced as a by-product.
The density of the rectangular block in g/mL is 7.0.
<u>Given the following data:</u>
- Mass of block = 22.8 gra1.94 kg
- Length of block = 3.21 cm
- Height of block = 1.84 in.
To find the density of the block in g/mL:
First of all, we would determine the volume of the rectangular block by using the following formula:
×
× 
<u>Conversion:</u>
1 in = 2.54 cm
5.83 in = X cm
Cross-multiplying, we have:

×
× 
Volume = 277.16 cubic centimeters.
<u>Note</u>: Milliliter (mL) is the same as cubic centimeters.
1000 grams = 1 kg
Y grams = 1.94 kg
Cross-multiplying, we have:
Y = 1940 grams
Now, we can find the density:

<em>Density </em><em>= 7</em><em>.0 g/mL</em>
Therefore, the density of the rectangular block in g/mL is 7.0.
Read more: brainly.com/question/18320053
Answer:
m H2(g) = 2.241 g H2(g)
Explanation:
- 2Al(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 3 H2(g)
limit reagent:
∴ Mw Al = 26.982 g/mol
∴ Mw H2SO4 = 98.0785 g/mol
⇒ n Al = (20 g Al)×(mol/26.982 g) = 0.7412 mol Al
⇒ n H2SO4 = ( 115 g H2SO4 )×(mol/98.0785 g) = 1.173 mol H2SO4
⇒ n H2 = (0.7412 mol Al)×(3 mol H2/ 2 mol Al) = 1.112 mol H2
∴ Mw H2 = 2.016 g/mol
⇒ g H2 = (1.112 mol H2)×(2.016 g/mol) = 2.241 g H2