The San Francisco earthquake of $1906$ measured magnitude $8.3$ on the Richter scale. Shortly afterward, an earthquake in South America had an intensity ratio four times greater than the San Francisco earthquake. Find the magnitude on the Richter scale of the earthquake in South America (up to one decimal point) $\left(\text{Use} {\log }_{10}4=0.6020\right)$

The $pH$ value of a solution is used to determine whether a solution is basic (alkaline) or acidic. A $pH$ value of $7$ is neutral, less than $7$ is acidic, and more than $7$ is basic. To calculate the $pH$ of a liquid you need to know the concentration of hydrogen ions $\left(H^{+}\right)$ in moles per litre (mol/l) of the liquid. The $pH$ is then calculated using the logarithmic formula: $pH=-{\log }_{10}\left(H^{+}\right)$.

Milk has $H^{+}=1.58\times {10}^{-7} \text{mol/l}$. Determine whether milk is acidic or basic. [Use $\log 1.58=0.198$]

The $pH$ value of a solution is used to determine whether a solution is basic (alkaline) or acidic. A $pH$ value of $7$ is neutral, less than $7$ is acidic, and more than $7$ is basic. To calculate the $pH$ of a liquid you need to know the concentration of hydrogen ions $\left(H^{+}\right)$ in moles per litre (mol/l) of the liquid. The $pH$ is then calculated using the logarithmic formula: $pH=-{\log }_{10}\left(H^{+}\right)$.

Find the $pH$ of vinegar with concentration: $H^{+}=1.58\times {10}^{-3} \text{mol/l}$. [Use $\log 1.58=0.198$]

The $pH$ value of a solution is used to determine whether a solution is basic (alkaline) or acidic. A $pH$ value of $7$ is neutral, less than $7$ is acidic, and more than $7$ is basic. To calculate the $pH$ of a liquid you need to know the concentration of hydrogen ions $\left(H^{+}\right)$ in moles per litre (mol/l) of the liquid. The $pH$ is then calculated using the logarithmic formula: $pH=-{\log }_{10}\left(H^{+}\right)$.

A sample of pool water has concentration: $H^{+}=6.3\times {10}^{-7} \text{mol/l}$. Determine the $pH$ of the sample of pool water. [Use $\log 6.3=0.778$]

The $pH$ value of a solution is used to determine whether a solution is basic (alkaline) or acidic. A $pH$ value of $7$ is neutral, less than $7$ is acidic, and more than $7$ is basic. To calculate the $pH$ of a liquid you need to know the concentration of hydrogen ions $\left(H^{+}\right)$ in moles per litre (mol/l) of the liquid. The $pH$ is then calculated using the logarithmic formula: $pH=-{\log }_{10}\left(H^{+}\right)$.

Some chemicals are added to the water. A sample of water is taken after adding the chemicals, and now the concentration is $H^{+}=7.94\times {10}^{-8} \text{mol/l}$. Determine if the water is now within optimal levels: $7.0<pH<7.4$. [Use $\log 7.94=0.899$]