Questions posted in Chemistry -

Questions posted in Chemistry

Shows quantities and how they vary by other factors A. bar graph B. line graph. C. circle graph

A. bar graph would be the closest

ANSWERED AT 02/06/2020 - 02:03 AM

QUESTION POSTED AT 02/06/2020 - 02:03 AM

Metamorphic rocks can be formed by __________.

Metamorphic rocks can be formed from any other type of rock - sedimentary or igneous. Remember these two examples of common metamorhpic rocksand where they come from: slate is formed from shale. marble is formed from limestone.

ANSWERED AT 02/06/2020 - 02:02 AM

QUESTION POSTED AT 02/06/2020 - 02:02 AM

Why is air considered a mixture not a compound?

The best reason I can think of for why we believe that air is a mixture is that freezing air slowly yields different liquids at different temperatures. Liquid nitrogen has a different boiling point than liquid oxygen. They also freeze at different temperatures. If air were only 1 compound, then air in its entirety would have a single boiling point and a single freezing point. 

ANSWERED AT 02/06/2020 - 02:01 AM

QUESTION POSTED AT 02/06/2020 - 02:01 AM

A substance composed of two or more elements in a fixed, definite proportion is a.a homogeneous mixture. b.a heterogeneous mixture. c.a compound. d.a solution. alloy.

A compound

(i think) because it consists of two + elements, whose ratios are shown clearly in the chemical formula, meaning it has a fixed, definite proportion. 

hope that helps :)

ANSWERED AT 02/06/2020 - 01:58 AM

QUESTION POSTED AT 02/06/2020 - 01:58 AM

Describe how oxidation and reduction involve electrons, change oxidation numbers, and combine in oxidation-reduction reactions.

The process of oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom or ion and reduction is the gain of electrons or a decrease in oxidation state. The oxidation number is the total number of electrons that an atom gains or loses in order to form a chemical bond with another atom. Redox reactions are electron transfer processes and include all chemical reactions in which atoms have their oxidation state changed. 

ANSWERED AT 02/06/2020 - 01:42 AM

QUESTION POSTED AT 02/06/2020 - 01:42 AM

Which statement best describes the change that is associated with the enthalpy of solution? Each step of the process is exothermic when the enthalpy of solution is negative. Each step of the process is endothermic when the enthalpy of solution is positive. Two steps of the process are exothermic, and one step is endothermic. Two steps of the process are endothermic, and one step is exothermic.

The correct option is D. Enthalpy of solution is defined as the heat change associated with the dissolution of a substance in a solvent at constant pressure leading to infinite dilution. Dissolution usually occur in three steps:
1. breaking of the inter- molecular forces which holds the molecules of the substance to be dissolved together. This reaction is endothermic.
2. the breaking of the inter molecular forces which the particles of the solvent together. This reaction is also endothermic.
3. the formation of attraction between the solute and the solvent. This reaction is exothermic.
Thus, out of the three steps of the reaction, two are endothermic while one is exothermic.

ANSWERED AT 02/06/2020 - 01:41 AM

QUESTION POSTED AT 02/06/2020 - 01:41 AM

Calculate the mass of excess reagent remaining at the end of the reaction in which 90.0 g of SO2 are mixed with 100.0 g of O2

We have to first write a balanced equation.
so2 + o2 -> so3

this is not balanced though. we have 3 oxygen on right and 4 on left
2so2 + o2 -> 2so3

now it is same on both sides. we have to figure out which is limiting reagent with the given amounts of reagents. we do this by comparing the ratio between them in terms of moles. we see that so2 has a coefficient of 2 and o2 has none which implies 1 and so3 has 2. this means that for every 2 moles of so2 reacting with 1 mole of o2, we get 2 moles of so3.

lets convert the given values to moles. to do this we know that molecular weight is measured in grams per mole. we are given grams and need to cancel out the grams to get moles. so the molecular weight:
so2 =32.1 + 2 * 16 = 64.1 g/mol
o2 = 2 * 16 = 32 g/mol
so3 = 32.1 + 3 * 16 = 80.1 g/mol

now to convert 90 g of 2so2 under ideal conditions.
90g / 64.1g/mol = 1.404 moles

convert this amount of moles of so2 to moles of o2. we have 2 moles of so2 to 1 of o2
1.404moles so2 / 2 moles so2 * 1 mole o2= 0.702 moles o2

so we see under ideal conditions that 90g of so2 would react with .702g of o2. lets see how many we actually have with 100g of o2
100g / 32g/mol =3.16 mol.

so we have a lot more o2 than needed. we are looking for how much is left in grams. we have to figure out how much was used. to do this convert our ideal moles of o2 into grams.
.702 moles o2 * 32g/mol = 22.5g o2

so what we startrd with (100g) minus what we needed (22.5g) is what we have left
100 - 22.5 = 77.5g o2

ANSWERED AT 02/06/2020 - 01:40 AM

QUESTION POSTED AT 02/06/2020 - 01:40 AM

Eye and hair color are examples of what? Alleles Genotypes Genes Phenotypes Polymorphisms

 the anwser is genotypes which is a personal characsteristic such as skin color eye or hair color or height

ANSWERED AT 02/06/2020 - 01:37 AM

QUESTION POSTED AT 02/06/2020 - 01:37 AM

Which pairing below does not correctly match the scientist with the contribution to the understanding of the atom? A. Proust and the realization that the elements of compounds are found in certain proportions by mass B. Rutherford and the understanding that the atom has a small, dense nucleus with a positive charge C. Thomson and the law of definite proportions D. Dalton and the initial proposal of the atomic theory of matter

The answer would be C. In fact, letter A already defines the Law of Definite Proportions. On the other hand, J.J. Thomson was responsible for the discovery of electrons through cathode ray tube experiments. The rest of the choices are true.

ANSWERED AT 02/06/2020 - 01:36 AM

QUESTION POSTED AT 02/06/2020 - 01:36 AM

What volume of 0.3682 M H2SO4 solution is required to react with 0.4198 grams of Al(CN)3 according to the reaction, 2 Al(CN)3 + 3 H2SO4  6 HCN + Al2(SO4)3?

According to this reaction, the ratio between Al(CN)3 and H2SO4 is 2:3. Knowing the molarity of H2SO4, in order to find out the volume we need to find out the moles of H2SO4 first.

Molar mass of Al(CN)3 is 26.98+(12.01+14.01)*3 = 105.04 g/mol.  So the moles of Al(CN)3 reacted = mass/molar mass = 0.4198g/105.04g/mol = 0.003997mol. According to the above ratio, the moles of H2SO4 = 0.003997mol*3/2 = 0.005995mole. 

The volume of H2SO4 needed for the reaction = moles of H2SO4/molarity of H2SO4 = 0.005995mole/0.3682mol/L = 0.01628L = 16.28 mL

ANSWERED AT 02/06/2020 - 01:34 AM

QUESTION POSTED AT 02/06/2020 - 01:34 AM

Which of the following correctly describes how rate laws are determined? Rate laws can be determined from the coefficients of balanced equations. The rate law for an elementary step can only be determined from unimolecular reactions. The rate law for the overall reaction is always determined by the rate law of the fastest step. Rate laws are determined through experimentation.

To answer this question, we must go through a process of elimination.

A. This is only true for elementary reactions; It does not apply to all.
B. This is not only applicable to unimolecular but to bimolecular and so on and so forth.
C. The contrary is true. The slowest reaction would be the basis because it is the rate-limiting step.
D. This is true.

The answer is D.

ANSWERED AT 02/06/2020 - 01:33 AM

QUESTION POSTED AT 02/06/2020 - 01:33 AM

Which of the following is a sign of a chemical reaction?

Color change , temp. change ,if a solid forms , umm there's probably more but that's all I remember

ANSWERED AT 02/06/2020 - 01:33 AM

QUESTION POSTED AT 02/06/2020 - 01:33 AM

What kinds of bonds make up a formula unit of sodium chloride? a. Ionic bonds c. 1 ionic bond and 1 covalent bond b. Covalent bonds d. Van der Waals forces

Ionic Bond

Ionic bonding is the bonding between metals and non-metals
Sodium, Na  is a metal
Chlorine, Cl  is a non-metal

Covalent bonding is the bonding between non-metals and non-metals

ANSWERED AT 02/06/2020 - 01:29 AM

QUESTION POSTED AT 02/06/2020 - 01:29 AM

Which of the following is not a property of a base? Please explain your answer. Change red litmus to blue Feel slippery to the touch Produce OH- ions Have a sour taste

Have a sour taste. because it should taste bitter. acid taste sour.

ANSWERED AT 02/06/2020 - 01:24 AM

QUESTION POSTED AT 02/06/2020 - 01:24 AM

You have 75.0 mL of a 2.50 M solution of Na2CrO4(aq). You also have 125 mL of a 1.79 M solution of AgNO3(aq). Calculate the concentration of CrO42– after the two solutions are mixed together.

The reaction of Na2CrO4 (aq) and AgNO3 (aq) is as follows:
2AgNO3 (aq) +Na2CrO4 (aq) ⇒Ag2CrO4 (s) + 2NaNO3 (aq).

During this reaction, part of the CrO42- reacts with Ag+ and precipitates out of the solution, part of the CrO42- (excess amount) remains in the solution. 

To find out how much CrO42- is reacted:
Moles of initial CrO42- = 0.075 L * 2.5 M = 0.1875 mole
Moles of initial Ag+ = 0.125 L * 1.79 M = 0.2238 mole

The reaction ratio between CrO42- and Ag+ is 1:2 according to the equation.  So moles of CrO42- that is reacted is 0.2238 mole/2 = 0.1119 mole.  Therefore, moles of CrO42- that remains in the solution is 0.1875mole-0.1119mole = 0.0756 mole

So the final concentration of CrO42- in the solution is 0.0756mole/(0.075L+0.125L)= 0.378 M.

ANSWERED AT 02/06/2020 - 01:19 AM

QUESTION POSTED AT 02/06/2020 - 01:19 AM

2.998x10^8 m/s is how many kilometers per hour

1.079 x 10⁹ km/h

Further explanation

2.998 x 10⁸ m/s has been known as the speed of light.

Let us convert the unit m/s to km/hour.

Change in unit length:

If 1 km = 1,000 cm, then \boxed{ \ 1 \ cm = 0.001 \ km \ } \rightarrow \boxed{ \ 1 \ cm = 10^{-3} \ km \ }

Change in unit time:

If \boxed{ \ 1 \ hour = 60 \ minutes = 3,600 \ seconds \ }, then \boxed{ \ 1 \ second = \frac{1}{3,600} \ hours \ }

The Process:

\boxed{ \ 2.998 \times 10^8 \ \frac{m}{s} \times \frac{10^{-3} \ km}{1 \ m} \times \frac{1 \ s}{\frac{1}{3,600} \ hours} \ }

\boxed{ \ 2.998 \times 10^8 \times 10^{-3} \ km \times \frac{3,600}{hours} \ }

\boxed{ \ 10,792.8 \10 \times 10^5 \ \frac{km}{hour} \ }

Remember, we must write the results in scientific notation, i.e.,

\boxed{\ a \times 10^b \ } \rightarrow \boxed{ \ 1 \leq a < 10 \ } \rightarrow \boxed{ \ b \ must \ be \ an \ integer \ }

Thus the result of unit conversion is

\boxed{ \ \boxed{ \ 2.998 \times 10^8 \ m/s \ } \rightarrow \boxed{ \ 1.079 \times 10^9 \ km/h} \ }

Learn more

  1. What unit conversion factor would you use in order to calculate its displacement in cubic-inches
  2. Does Marcus pay tax?
  3. Express your answer numerically in US dollars to three significant figures.

Keywords: speed of light, convert, m/s to km/h, unit length, time, hours, minutes, second, scientific notation

ANSWERED AT 02/06/2020 - 01:19 AM

QUESTION POSTED AT 02/06/2020 - 01:19 AM

When the government is preparing for a natural disaster, how would science aid in decision-making?

They would recommend all of the probabilities and outcomes of the disaster

ANSWERED AT 01/06/2020 - 04:49 PM

QUESTION POSTED AT 01/06/2020 - 04:49 PM

Elements that can have several different structures with different physical properties are called?

Liquid for sure,
all i can think off

ANSWERED AT 01/06/2020 - 04:48 PM

QUESTION POSTED AT 01/06/2020 - 04:48 PM

Dalton assumed that all atoms of the same element were identical in all their properties. Explain why this assumption is not valid.

This assumption is not valid because, there are some elements which exist in two or more forms;  they have the same atomic number but differ in their mass number, which meas that they possess different number of neutrons. These type of element are called isotopes. Isotope have the same atomic number  and similar physical and chemical properties but they have different number of neutrons and therefore possess different masses.  

ANSWERED AT 01/06/2020 - 04:45 PM

QUESTION POSTED AT 01/06/2020 - 04:45 PM

Nuclear fission: A produces less waste than fusion B creates more air pollution than burning fossil fuels C often causes thermal pollution of water sources D all of the above

The answer is A because it cant pollute the atmosphere because its vapor from water that is being thrown out and it is reusable / the chemical reaction last longer

ANSWERED AT 01/06/2020 - 04:45 PM

QUESTION POSTED AT 01/06/2020 - 04:45 PM

Is Octylphenol ethoxylate a solvent or solute


its a solute


ANSWERED AT 01/06/2020 - 04:44 PM

QUESTION POSTED AT 01/06/2020 - 04:44 PM

One part phosphorus nine Parts potassium make up this compound that was recently isolated from dog urine

Cocaine m8 cocaine you should try it

ANSWERED AT 01/06/2020 - 04:44 PM

QUESTION POSTED AT 01/06/2020 - 04:44 PM

Which layer underground where all empty spaces are filled with a combination of air and water

The correct effin answer is zone of aeration

ANSWERED AT 01/06/2020 - 04:42 PM

QUESTION POSTED AT 01/06/2020 - 04:42 PM

A ____ property is a characteristic of a substance that can be observed and does not change the identity of a substance

A physical property. Hope this helps.

ANSWERED AT 01/06/2020 - 04:40 PM

QUESTION POSTED AT 01/06/2020 - 04:40 PM

If two atoms are bonded with a bond energy of 87 kJ, what must be done to break the bond? A. 87 kJ of energy must be added B. The energy must be decreased by 87 kJ. C. The bond order has to be higher. D. No energy should come out or go in.

I would say the energy has to be decreased by 87 kj because the bonding is held together by 87 kj so removing that should prevent the bonding from taking place or reverse it I believe. In other words, a certain amount of energy is required to hold the bond together and in the absence of that energy, the bonding will not take place.

ANSWERED AT 01/06/2020 - 04:38 PM

QUESTION POSTED AT 01/06/2020 - 04:38 PM

Can anyone tell me what is bioluminescence is?

The biochemical emission of light by living organisms such as fireflies and deep-sea fishes.

ANSWERED AT 01/06/2020 - 04:37 PM

QUESTION POSTED AT 01/06/2020 - 04:37 PM

J.C. wants to determine if there is a relationship between room color and sleep. Based on his research, J.C. makes an educated guess that people fall asleep more quickly in a room painted blue than in a room painted yellow. He asks several people which color they like better, yellow or blue, and uses their responses to see if his educated guess was correct. What is missing from J.C.'s scientific investigation? a. experiement testing hypothesis b. research on topic to see what others learned. c.hypothesis based on research that can be tested d.analysis of responses from all test subjects

What is missing from JC's scientific investigation is AN HYPOTHESIS BASED ON RESEARCH THAT CAN BE TESTED. The correct option is C. In order to determine the relationship between two parameters in a research one has to formulate an hypothesis which can be tested out physically to validate its authenticity. This will give other scientists the opportunity to reproduce the research in any part of the world in order to verify its results.

ANSWERED AT 01/06/2020 - 04:37 PM

QUESTION POSTED AT 01/06/2020 - 04:37 PM

Which of the following is not an example of a science? a.geology b.astrology c.astronomy d.ecology

I think it is b.astrology

ANSWERED AT 01/06/2020 - 04:35 PM

QUESTION POSTED AT 01/06/2020 - 04:35 PM