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Midterm Review Do- Nows. Chemistry CP 2011-2012. Copy and answer the questions below:. 1. Convert -240°C to Kelvin. 2. A student decomposes 123g of KClO 3 . After the reaction, he measures 75g of KCl in the container. How many grams of O 2 were released? Which law is this?

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midterm review do nows

Midterm Review Do-Nows

Chemistry CP

2011-2012

copy and answer the questions below
Copy and answer the questions below:
  • 1. Convert -240°C to Kelvin.
  • 2. A student decomposes 123g of KClO3. After the reaction, he measures 75g of KCl in the container. How many grams of O2 were released? Which law is this?

2 KClO3 2KCl + 3 O2

slide3

123g = 75g + X

123g – 75g = X

X = 48g

Law of Conservation of Matter

-240°C + 273° = 33K

slide4

Copy and answer the questions below:

A student does an experiment to find the amount of heat released when different masses of sodium hydroxide dissolve in water. His data are given below:

1. Identify the independent and dependent variables.2. Which mass has the greatest precision? EXPLAIN.3. The correct heat for 1g is 225cal. How is the student’s accuracy? EXPLAIN.

slide5

The independent variable is the mass of sodium hydroxide.

The dependent variable is the amount of heat released.

1g had the greatest precision. The values are most alike.

The accuracy is not very good. Accuracy is how far the answer is from the accepted value. The average experimental value is 202 cal, which is not close to 225 cal.

slide6

Copy and answer the questions below:

1. Arrange the following in order of increasing frequency: X-ray, Gamma Rays, Radio Waves2. If the energy of a wave doubles, what happens to the frequency?3. If the energy of a wave doubles, what happens to the wavelength?

slide7

Radio < X-ray < Gamma

The frequency also doubles.

The wavelength is cut in half.

slide8

Copy and answer the questions below:

The half-life of an isotope of uranium is 14.0 minutes. What mass of a 200g sample of the isotope will remain after 56 minutes?

Complete the following nuclear equations:

slide9

56/14 = 4

2. 200g  100g  50g  25g  12.5g 12.5g

slide10

Copy and answer the questions below:

Element X has three isotopes. Their masses and relative abundance are listed below. Find the atomic mass of element X.

Isotope 1 mass = 42.5amu abundance = 23%

Isotope 2 mass = 40.1amu abundance = 58%

Isotope 3 mass = 43.5amu abundance = 19%

What is an isotope?

What is an ion?

slide11

42.5 x 23 + 40.1 x 58 + 43.5 x 19 = 4129.8

4129.8 / 100 = 41.298 amu

Isotopes are atoms of the same element with a different mass. This means they have the same atomic number (protons), but a different number of neutrons.

Ions are charged particles. They have a different number of protons than electrons.

slide12

Copy and answer the questions below:

STUDY THE LIST OF ELEMENTS BELOW:

Si, Xe, Ar, Rb, I, Al

Answers can be used more than once or not at all!

Which of the elements above:

Has the largest radius?

Forms a +1 ion?

Forms a +3 ion?

Has the greatest electronegativity?

Has the greatest ionization energy?

Is diatomic?

Is a metalloid?

Forms a -1 ion?

slide13

STUDY THE LIST OF ELEMENTS BELOW:

Si, Cl, Ar, Rb, Xe, Al

Answers can be used more than once or not at all!

  • Which of the elements above:
  • Has the largest radius? Rb
  • Forms a +1 ion? Rb
  • Forms a +3 ion? Al
  • Has the greatest electronegativity? Cl
  • Has the greatest ionization energy? Ar
  • Is diatomic? Cl
  • Is a metalloid? Si
  • Forms a -1 ion? Cl
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