CHEMISTRY HIGH SCHOOL

The elements in Period 5 on the Periodic Table are arranged from left to right in order of(1) decreasing atomic mass(2) decreasing atomic number(3) increasing atomic mass(4) increasing atomic number

Answers

Answer 1
Answer:

Answer: Option (4) is the correct answer.

Explanation:

Atomic mass of an atom or element means the total number of protons and total number of neutrons present.

Whereas atomic number means the total number of protons present in an atom or element.

In period 5 on the Periodic Table, elements from left to right are arranged in order of increasing atomic number.

On the other hand, the atomic mass is not increasing from left to right.

Answer 2
Answer: Going from left to right, they are ordered by increase in atomic number

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Which type of stoichiometric calculation does not require the use of the molar mass?

Answers

The choices can be found elsewhere and as follows:

a. mass-mass problems 
b. mass-volume problems 
c. mass-particle problems 
d. volume-volume problems

I believe the correct answer is option D. It is volume-volume problems that does not require the use of molar mass.  Here you are dealing with molarities and volumes to determine concentrations. Molar mass is not part of any calculations.

Final answer:

The type of stoichiometric calculation that does not require the use of the molar mass is a calculation involving molar or stoichiometric ratios which are derived directly from the coefficients in a balanced chemical equation.

Explanation:

In stoichiometry, there are several types of calculations that can be performed. However, the type of stoichiometric calculation that does not require the use of the molar mass is the calculation involving the molar ratio, or stoichiometric ratio. This refers to the ratio of coefficients in a balanced chemical equation, which we use to determine the relative amounts of each substance involved in a chemical reaction.

An example of this is a balanced equation for the formation of water: H2 + 0.5O2 -> H2O. In this equation, the molar or stoichiometric ratio of hydrogen (H2) to oxygen (O2) to water (H2O) is 2:1:2. If we are given the number of moles of one substance, we can use this molar ratio to find the number of moles of any other substance in the equation, without needing to know their molar masses. This constitutes a stoichiometric calculation without the need for molar mass.

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A pH of 2 indicates a(n) _____.

Answers

A pH of 2 indicates a acid

The falling of rain, snow, hail, or ice pellets from the atmosphere is called watering

precipitation

perception

Answers

Precipitation is when water falls from the clouds in one form or another.
Watering isn't the right term.
Perception is seeing something.

Answer:

Precipitation

Explanation:

How many molecules are in 0.25 mole of O2

Answers

According to the concept of Avogadro's number, there are 1.505×10²³ molecules in 0.25 mole of O₂.

What is Avogadro's number?

Avogadro's number is defined as a proportionality factor which relates number of constituent particles with the amount of substance which is present in the sample.

It has a SI unit of reciprocal mole whose numeric value is expressed in reciprocal mole which is a dimensionless number and is called as Avogadro's constant.It relates the volume of a substance with it's average volume occupied by one of it's particles .

According to the definitions, Avogadro's number depend on determined value of mass of one atom of those elements.It bridges the gap between macroscopic and microscopic world by relating amount of substance with number of particles.

Number of atoms can be calculated using Avogadro's number as follows: mass/molar mass×Avogadro's number

Number  of molecules is obtained by multiplying number of moles and Avogadro's number , that is 0.25×6.023×10²³=1.505×10²³ molecules.

Thus, there are 1.505×10²³ molecules in  in 0.25 mole of O₂.

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1 mole O2 -------------------- 6,02.10²³ molecules
0,25 mole O2 ---------------- x molecules

1 . x = 0,25 . 6,02.10²³

x = 1,50.10²³ molecules

To prevent accidental poisoning, you should NOT __________.a. mix chemicals in well ventilated areas
b. follow the instructions on the label
c. keep materials in unlabeled containers
d. use chemicals in well ventilated areas

Answers

Answer: option C. keep materials in unlabeled containers.


Justification:


Indeed, keeping materials in unlabeled containers is a risky, dangerous, bad practice.


Labels should be according to international standards. That is, further to the name of the product, labels must signal the danger associated with the product: whether it is poison, toxic, flammable, acid, caustic, explosive, or harmful to the body or the enviroment.


On the other hand, the other options, a. mix chemicals in well ventilated areas, b. follow the instructions on the label, and d. use chemicals in well ventilated areas, are good safety practices, among many others.

Answer: C

Explanation:

Keep materials in unlabeled containers

The cheetah has been clocked at 112 km/Hr. What speed would this be in ft/sec?

Answers

All you have to do in convert two units. You need to know that there are 3600 seconds in an hour, and one kilometer is ~3,280.8399 feet. 3,280.8399 * 112 is equal to 367454.0688 feet per hour. Now divide it by 3600 to get it into seconds. That is equal to 102.07057466666667 feet per second. That's your answer.
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