91Ó°ÊÓ

Concentration is defined as the abundance of an ingredient divided by the total volume of a mixture in chemistry.

Uncertainty refers to the range of probable values in which the measurement's true value can be found.

We are given the following:

Total volume of solution$=10mL$

The mass of dissolved tooth$=0.75mg$

First, we'll plot the extra Sr Vs signal using the table provided:

Using the equation of the straight line, the concentration ofSris found whenyequals0, so:

y=(3.136x)+27.36 0=(3.136x)+27.36 x=-8.72ng/mL

The negative sign indicates that the point is located in the negativex-axis.

The standard uncertainty of the $x$-intercept is expressed in the below equation:

$u_x=\frac{s_y}{\left|m\right|}×\sqrt{\frac{1}{n}+\frac{y^{-2}}{m^2×\underset{}{∑}{\left(x_i-x\right)}^2}}$

Where:

syis the standard deviation

|m|is the absolute value of the slope

nis the number of data points

yis the mean value ofy

x_iis the individual values ofX

xis the mean value ofx

After calculating the above values using excel:

$u_x=0.43ppb$

The concentration of Sr found in parta=8.72ng/mL

Since the volume of solution is10mL:

Mass ofSr=8.72ng/mL10mL=87.2ng

The mass of dissolved tooth is given in the question, so to find the concentration(m/m)ing/g

$\frac{87.2ng}{0.75mg}×\frac{1mg}{1000g}×\frac{1000\mathrm{μ}g}{1ng}=116.27g/g$

The concentration of Sr found in part a=8.72ng/mL

Since the volume of solution is10mL:

$MassofSr=(8.72ng/mL0.43)10mL=87.2ng4.3$

The mass of dissolved tooth is given in the question, so to find the concentration(m/m)in$\mathrm{μ}$g/g

$\frac{87.2ngÂ\pm 4.3}{0.75mg}×\frac{1mg}{1000g}×\frac{1000g}{1ng}=122g/g=116.27g/g5.73ppm$

The95%confidence interval is found through the below equation:

- Using table 4.4,t=3.182

-sis calculated in part (c)

confidence interval$=Â\pm t×s=Â\pm 3.182×5.73=18.2ppm$