Question

chemistry: unit #1 exam study guide

• how many milligrams are in 15 kg?

1.5e+7

• list the metric units below:
• the number of seconds in a 35 - hour work week can be as:
• what is the volume of 20.0 g of ether if the density of ether is 0.70 g/ml?
• the temperature reading of - 37 °c corresponds to a kelvin reading of:
• concentrated hydrochloric acid has a density of 1.19 g/ml. what is the mass, in grams, of 350 milliliters of this acid?
• a student measures a volume as 20.0 ml, whereas the correct volume is 18.5 ml. what is the percent error?
• the number of significant figures in 7.0135 is:
• the number of significant figures in value 0.00009671 is:
• what is the number of significant figures in 400.00?
• the mass of a ball is recorded at 3.659873256 kg. round this number to 4 significant figures.
• a fish tank at a pet store has the dimensions 6.8 cm, 9.6 cm and 17.2 cm. the volume of water (in cm³) that can be stored in tank (correct up to four significant figures) is:
• what are the 3 main phases of matter?
• when paper and oxygen combine to form carbon dioxide and water, what occurs?
• what is the proper scientific notation for 0.00758?

Explanation:

Step1: Convert kilograms to milligrams

We know that 1 kg = 1000 g and 1 g= 1000 mg, so 1 kg = 1000×1000 mg = 10^6 mg. For 15 kg, the number of milligrams is 15×10^6 mg = 1.5×10^7 mg.

Step2: List metric units

Common metric units include meter (length), gram (mass), liter (volume), second (time), Celsius (temperature) etc.

Step3: Calculate seconds in 35 - hour work - week

1 hour = 3600 seconds. For 35 hours, the number of seconds is 35×3600 s=126000 s.

Step4: Find volume of ether

Using the formula $
ho=\frac{m}{V}$ (where $
ho$ is density, $m$ is mass and $V$ is volume), we can re - arrange it to $V = \frac{m}{
ho}$. Given $m = 20.0$ g and $
ho=0.70$ g/mL, then $V=\frac{20.0}{0.70}\text{mL}\approx28.6$ mL.

Step5: Convert Celsius to Kelvin

The conversion formula is $K = ^{\circ}C+ 273.15$. For $T=-37^{\circ}C$, $T = - 37+273.15$ K = 236.15 K.

Step6: Find mass of hydrochloric acid

Using $m=
ho V$, with $
ho = 1.19$ g/mL and $V = 350$ mL, then $m=1.19\times350$ g = 416.5 g.

Step7: Calculate percent error

The percent - error formula is $\text{Percent Error}=\frac{\vert\text{Measured Value}-\text{True Value}\vert}{\text{True Value}}\times100\%$. Here, Measured Value = 20.0 mL and True Value = 18.5 mL. So $\text{Percent Error}=\frac{\vert20.0 - 18.5\vert}{18.5}\times100\%=\frac{1.5}{18.5}\times100\%\approx8.1\%$.

Step8: Determine significant figures in 7.0135

All non - zero digits and zeros between non - zero digits are significant. So there are 5 significant figures.

Step9: Determine significant figures in 0.00009671

Leading zeros are not significant. So there are 4 significant figures.

Step10: Determine significant figures in 400.00

Trailing zeros after a decimal point are significant. So there are 5 significant figures.

Step11: Round to 4 significant figures

For 3.659873256 kg, rounding to 4 significant figures gives 3.660 kg.

Step12: Calculate volume of fish tank

The volume of a rectangular prism (fish tank) is $V=l\times w\times h$. Given $l = 6.8$ cm, $w = 9.6$ cm and $h = 17.2$ cm, then $V=6.8\times9.6\times17.2$ cm³=$6.8\times165.12$ cm³ = 1122.816 cm³$\approx1123$ cm³ (4 significant figures).

Step13: Name phases of matter

The three main phases of matter are solid, liquid and gas.

Step14: Identify chemical reaction

When paper and oxygen combine to form carbon dioxide and water, a chemical reaction (combustion) occurs.

Step15: Write scientific notation for 0.00758

In scientific notation, $0.00758 = 7.58\times10^{-3}$.

Answer:

1. 1.5×10^7 mg
2. Meter, gram, liter, second, Celsius etc.
3. 126000 s
4. 28.6 mL
5. 236.15 K
6. 416.5 g
7. 8.1%
8. 5
9. 4
10. 5
11. 3.660 kg
12. 1123 cm³
13. Solid, liquid, gas
14. A chemical reaction (combustion)
15. 7.58×10^{-3}