Question

1. a rubber stopper has a mass of 7.452 g and displaces 6.0 ml of water in a graduated cylinder. refer to example exercise 2 and calculate the density of the rubber stopper.
2. state the length shown for each of the following rectangular solids.
3. an unknown rectangular solid has a mass of 140.417 g and measures 5.05 cm by 2.50 cm by 1.25 cm. refer to example exercise 3 and calculate the density of the unknown solid.
4. an aluminum foil weighs 0.465 g and measures 10.10 cm by 10.05 cm. given the density of aluminum, 2.70 g/cm³, refer to example exercise 4 and calculate the thickness of the foil.
5. what safety precautions must be observed in this experiment?

Explanation:

Step1: Recall density formula

The density formula is $
ho=\frac{m}{V}$, where $
ho$ is density, $m$ is mass and $V$ is volume.

Step2: Calculate density of rubber stopper

Given $m = 7.452\ g$ and $V=6.0\ mL$. Substitute into the formula: $
ho=\frac{7.452\ g}{6.0\ mL}=1.242\ g/mL$.

Step3: Calculate volume of rectangular - solid in question 6

The volume of a rectangular solid $V = l\times w\times h$. Given $l = 5.05\ cm$, $w = 2.50\ cm$ and $h = 1.25\ cm$. So $V=5.05\times2.50\times1.25=15.78125\ cm^{3}$.

Step4: Calculate density of rectangular - solid in question 6

Using $
ho=\frac{m}{V}$, with $m = 140.417\ g$ and $V = 15.78125\ cm^{3}$. Then $
ho=\frac{140.417\ g}{15.78125\ cm^{3}}\approx8.90\ g/cm^{3}$.

Step5: Recall density formula for question 7

We know $
ho=\frac{m}{V}$, and we can re - arrange it to $V=\frac{m}{
ho}$. Given $m = 0.465\ g$ and $
ho = 2.70\ g/cm^{3}$, so $V=\frac{0.465\ g}{2.70\ g/cm^{3}}\approx0.1722\ cm^{3}$.

Step6: Calculate thickness of aluminum foil

The volume of a rectangular - shaped foil $V=l\times w\times t$, where $t$ is thickness. Given $l = 10.10\ cm$ and $w = 10.05\ cm$. We can solve for $t$: $t=\frac{V}{l\times w}=\frac{0.1722\ cm^{3}}{10.10\ cm\times10.05\ cm}\approx0.0017\ cm$.

Answer:

1. Density of rubber stopper: $1.242\ g/mL$
2. Density of unknown rectangular solid: $\approx8.90\ g/cm^{3}$
3. Thickness of aluminum foil: $\approx0.0017\ cm$
4. For question 5, since no measurements are given in the text (only the ruler and solid are shown without indicating the start - end points for measurement), we cannot answer it.
5. Safety precautions: Wear safety goggles to protect eyes from any splashes or flying particles; handle solids carefully to avoid injury; if using chemicals (not mentioned here but in a general lab setting), follow proper chemical - handling procedures such as wearing gloves, and working in a well - ventilated area.