#### Answer

$3.12\times10^{-5}$

#### Work Step by Step

To convert a number from standard notation to scientific notation, we must move the decimal to the left or to the right, counting the number of places, until the number is between $1$ and $10$, and multiply by a power of $10$. If the number is less than $1$, and we moved the decimal to the right, the power of $10$ is the negative number of places we moved the decimal point. If the number is greater than $1$, and we moved the decimal to the left, the power of $10$ is the positive number of places we moved the decimal point.
When trying to convert $0.0000312$ to scientific notation, we have to move the decimal point to the right $5$ places. This gives us a coefficient of $3.12$, and our power of $10$ will be $-5$.
This gives us the expression: $3.12\times10^{-5}$