Answer:
D
Explanation:
As bioindicators are the organism that indicate or monitor the health of the environment
The density of a material is the mass of the material per unit volume. Here the weight of the same metal is 44.40g, 40.58g and 38.35g having volume 4.8 mL, 4.7 mL and 4.2 mL respectively. Thus the density of the metal as per the given data are,
= 9.25g/mL,
= 8.634g/mL and
= 9.130g/mL respectively.
The equation of the standard deviation is √{∑(x -
)÷N}
Now the mean of the density is {(9.25 + 8.634 + 9.130)/3} = 9.004 g/mL.
The difference of the density of the 1st metal sample (9.25-9.004) = 0.246 g/mL. Squaring the value = 0.060.
The difference of the density of the 2nd metal sample (9.004-8.634) =0.37 g/mL. Squaring the value = 0.136.
The difference of the density of the 3rd metal sample (9.130-9.004) = 0.126 g/mL. Squaring the value 0.015.
The total value of the squared digits = (0.060 + 0.136 + 0.015) = 0.211. By dividing the digit by 3 we get, 0.070. The standard deviation will be
. Thus the standard deviation of the density value is 0.265g/mL.
Answer:
0.0400 g for the example given below.
Explanation:
pH value is not provided, so we'll solve this problem in a general case and then we will use an example to justify it.
- By definition,
. - NaOH is a strong base, as it's a hydroxide formed with a group 1A metal, so it dissociates fully in water by the equation:
. - From the equation above, using stoichiometry we can tell that the molarity of hydroxide is equal to the molarity of NaOH:
. - Concentration of hydroxide is then equal to the ratio of moles of NaOH and the volume of the given solution. Moles themselves are equal to mass over molar mass, so we obtain:
. - We also know that
. Take the antilog of both sides:
. - Solve for the mass of NaOH:
.
Now, let's say that pH is given as 12.00 and we use a 100-ml volumetric flask. Then we would obtain:
