The answer is (C) 2 hydrogen atoms
Answer: 1.85M
Explanation:
Sodium hydroxide has a chemical formula of NaOH
Given that,
Amount of moles of NaOH (n) = ?
Mass of NaOH in grams = 63g
For molar mass of NaOH, use the molar masses:
Sodium, Na = 23g;
Oxygen, O = 16g;
Hydrogen, H = 1g
NaOH = (23g + 16g + 1g)
= 40g/mol
Since, amount of moles = mass in grams / molar mass
n = 63g / 40.0g/mol
n = 1.575 mole
Volume of NaOH solution (v) = 850mL
[Convert 850mL to liters
If 1000mL = 1L
850mL = 850/1000 = 0.85L]
Concentration of NaOH solution (c) = ?
Since concentration (c) is obtained by dividing the amount of solute dissolved by the volume of solvent, hence
c = n / v
c = 1.575 mole / 0.85L
c = 1.85M [1.85M is the concentration in moles per litres which is also known as molarity]
Thus, the molarity of the solution is 1.85M
Answer:
= 25 ppm
Explanation:
- PPM also refers to parts per million, it represents a low concentration of a solution. It represents 0.001 gram or a milligram in a 1000 mL, which equivalent to 1 mg per liter.
Given; a sample size of 2000 g contained 0.050 g DDT
It means, 2000 mL sample contained 50 mg DDT
Therefore in ppm we get;
= 50 mg/ 2 L
= 25 mg/L
<u>= 25 ppm</u>
In an average mass, each entry has equal weight. In a weighted average, we multiply each entry by a number representing its relative importance.
Assume that your class consists of 15 girls and 5 boys. Each girl has a mass of 54 kg, and each boy has a mass of 62 kg.
<em>Average mass</em> = (girl + boy)/2 = (54 kg + 62 kg)/2 = <em>58 kg</em>
<em>Weighted average (Method 1)
</em>
Use the <em>numbers of each</em> gender (15 girls + 5 boys)
,
Weighted average = (15×54 kg + 5×62 kg)/20 = (810 kg + 310 kg)/20
= 1120 kg/20 = <em>56 kg</em>.
If you put all the students on one giant balance, their total mass would be
1120 kg and the average mass of a student would be <em>56 kg.
</em>
<em>Weighted average (Method 2)
</em>
Use the <em>relative percentages</em> of each gender (75 % girls and 25 % boys).
Weighted average = 0.75×54 kg + 0.25×62 kg = 40.5 kg + 15.5 kg = <em>56 kg</em>
Each girl contributes 40.5 kg and each boy contributes 15.5 kg to the <em>weighted average</em> mass of a student.
