CHEMISTRY HIGH SCHOOL

The melting and freezing points of a substance are the same temperature.a. True
b. False

Answers

Answer 1
Answer: That's false. A melting point is hot/warm, while the freezing point is cold.
Answer 2
Answer: False! The melting point and freezing points would differ based on their properties. 

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An atom that has 84 protons and 86 neutrons undergoes a reaction. At the end of the reaction, it has 82 protons and 84 neutrons. What happened to the atom?

Answers

During a nuclear reaction, an atom must emit an alpha particle, which consists of 2 protons (positively charged) and 2 neutrons (neutrally charged). Thus, the alpha particle has a charge of +2 (there are no electrons, which are negatively charged, to balance out the two protons). When an atom emits an alpha particle, it will lose this particle, thus losing 2 protons and 2 neutrons as well. Since the atom in the equation goes from 84 protons to 82, and 86 neutrons to 84, it lost 2 protons and 2 neutrons, indicating that it emitted an alpha particle.

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Which model can be used to trace genetic inheritance

Answers

To tract genetic inheritance ( phenotype or genotype) from one generation to another generation, PEDIGREE CHART is used. Pedigree Chart is a diagram shows the occurrence and appearance of a particular genes of an individual organism from its ancestor down to the generations it follows. Relationship in a pedigree is shown as a series of linear graph. Parents are connected to a horizontal lines while vertical lines will lead to the offspring.

What happens when the number of electrons and protons inside of an atom are Not equel?

Answers

Hello, It's me Moriah Elizabeth!

Answer:

When the number of electrons does not equal the number of protons, the atom is ionized.

16 Which change results in the formation of different substances?(1) burning of propane(2) melting of NaCl (s)
(3) deposition of CO2(g)
(4) solidification of water

Answers

Answer:The correct answer is option (1).

Explanation:

Burning of propane in the presence of oxygen will form carbon-dioxide, water and heat.The chemical reaction can represented as in chemical equation:

C_3H_8+5O_2\rightarrow 3CO_2+4H_2O+heat

This is an example of chemical change where new product is formed.

Where as in melting of sold sodium chloride, deposition of carbon-dioxide gas and solidification of water ;phase of the substance is changing that is a physical change is taking place.

Hence, the correct option is (1).
1. The burning of propane creates different substances: propane and oxygen combine to create water and carbon dioxide:

C3H8 + 5 O2 becomes 3 CO2 + 4 H2O + heat

2. When NaCl melts, it is changing state, but it is still the same NaCl.

3. When gaseous CO2 deposits it is changing state, but it is still the same CO2.

4. When (presumably liquid) water solidifies, it is changing state, but it is still the same water.

So the answer is 1.

If it takes 65.3 min for the concentration of a reactant to drop to 20.0% of its initial value in a first-order reaction, what is the rate constant for the reaction in the units min-1?

Answers

65.3 / 20

equals 3.265

Consider the unbalanced equation for the combustion of hexane:2C6H14(g)+19O2(g)→12CO2(g)+14H2O(g)Determine how many moles of O2 are required to react completely with 7.9 moles C6H14.

Answers

The balanced equation is C6H14(g) + 19/2O2(g) → 6CO2(g) + 7H2O(g). If you are given 7.9 moles C6H14, multiply it by a ratio of 19/2/1 to get the moles of oxygen. Then, you will get 75.05 moles of O2.
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