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inysia [295]
3 years ago
7

4. A compact disc has a diameter of 11.8 cm. What is the surface area of the disc in square centimeters? In square meters? [Area

of a circle = (π)(radius) 2 ]
Chemistry
1 answer:
d1i1m1o1n [39]3 years ago
8 0
<span>The surface area is 109.3 square centimeters or 0.01093 square meters. The area formula requires that we use the radius of the disc. We can find the radius by diving the diameter by 2, so radius = 11.8/2 or 5.9 cm. We can use 3.14 as an approximation for π. The surface area is 3.14 * (5.9*5.9). Since the diameter is given in cm, the surface area units are in square centimeters. To convert to meters, divide any measurement in centimeters by 100, but we need to convert to "square" meters, so we need to divide our square centimeters by 100 * 100, or by 10,000. Dividing 109.3 by 10,000 results in 0.01093 square "meters".</span>
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Which of the following happens during an endothermic chemical change?
Ede4ka [16]

Answer:

products have a higher potential energy than the reactants

Explanation:

The total potential energy of the system increases for the endothermic reaction as the system absorbs energy from the surroundings. The total potential energy of the system decreases for the exothermic reaction as the system releases energy to the surroundings

4 0
2 years ago
Part B Identify the sets of quantum numbers that describe all the electrons in the ground state of a neutral beryllium atom, Be.
dmitriy555 [2]

<u>Answer:</u> The set of quantum numbers for the electrons in Be atom are (2, 1, -1, 1/2), (1, 0, 0, 1/2), (1, 0, 0, -1/2) and (2, 0, 0, -1/2)

<u>Explanation:</u>

There are 4 quantum numbers:

  • Principal Quantum number (n) specifies the energy of the electron in a shell.
  • Azimuthal Quantum number (l) specifies the shape of an orbital. The value of it lies in the range of 0 to (n-1)
  • Magnetic Quantum number (m) specifies the orientation of the orbital in space. The value of it lies in the range of -l to +l
  • Spin Quantum number (s) specifies the spin of an electron in an orbital. It can either have a value of +\frac{1}{2} or -\frac{1}{2}

Berylium (Be) is the 4th element of periodic table having electronic configuration of 1s^22s^2

  • <u>For electrons in 1s-orbital, the quantum numbers can be:</u>

For first electron:

n=1\\l=0\text{ (for s-subshell)}\\m=0\\s=+\frac{1}{2}

For second electron:

n=1\\l=0\\m=0\\s=-\frac{1}{2}

  • <u>For electrons in 2s-orbital, the quantum numbers can be:</u>

For first electron:

n=2\\l=0\text{ (for s-subshell)}\\m=0\\s=+\frac{1}{2}

For second electron:

n=2\\l=0\text{ (for s-subshell)}\\m=0\\s=-\frac{1}{2}

Hence, the set of quantum numbers for the electrons in Be atom are (2, 1, -1, 1/2), (1, 0, 0, 1/2), (1, 0, 0, -1/2) and (2, 0, 0, -1/2)

4 0
3 years ago
What happens when you shoot a neutron at a uranium-238 atom?
serious [3.7K]

Answer: Scientist shoot a whole bunch of neutrons at uranium-235 atoms. When one neutron hits the nucleus the uranium becomes U-236. When it becomes 236, the uranium atoms wants to spilt apart. After it splits it gives off three neutrons and a lot of energy.

Explanation:

7 0
3 years ago
1. Complete the balanced dissociation equation for the compound below. If the compound does not dissociate, write NR after the r
puteri [66]

Answer:

1. (NH₄)₂S(s) -----> NH₄+(aq) + S²-(aq)

2. Al³+ (aq) + PO₄³+ (aq) ----> AlPO₄ (s)

Explanation:

The dissociation of ammonium sulphide, (NH₄)₂S when dissolved in water is given in the equation below:

(NH₄)₂S(s) -----> NH₄+(aq) + S²-(aq)

However very little S²- ions are present in solution due to the very basic nature of the S²- ion (Kb = 1 x 105).

The ammonium ion being a better proton donor than water, donates a proton to sulphide ion to form hydrosulphide ion which exists in equilibrium with aqueous ammonia.

S²- (aq) + NH₄+ (aq) ⇌ SH- (aq) + NH₃ (aq)

Aqueous solutions of ammonium sulfide are smelly due to the release of hydrogen sulfide and ammonia, hence, their use in making stink bombs.

2. The reaction between aluminium nitrate and sodium phosphatein aqueous solution is a double decomposition reaction whish results in the precipitation of insoluble aluminium phosphate. The equation of the reaction is given below :

Al(NO₃)₃ (aq) + Na₃PO₄ (aq) ----> AlPO₄ (s) + 3 NaNO₃ (aq)

The net ionic equation is given below:

Al³+ (aq) + PO₄³+ (aq) ----> AlPO₄ (s)

7 0
2 years ago
How does mass and volume affect sinking and floating? Please don't plagiarize.... ​
Firdavs [7]

Answer:

If an object has a higher density than the fluid it is in (fluid can mean liquid or gas), it will sink. If it has a lower density, it will float. Density is determined by an object's mass and volume. If two objects take up the same volume, but have one has more mass, then it also has a higher density.

Explanation:

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