what might happen to variables in a science experiment that would lead to unusable results?

Answer:

I literally got this from google.

Explanation:

In ordinary air, sodium metal reacts to form a sodium hydroxide film, which can rapidly absorb carbon dioxide from the air, forming sodium bicarbonate. ... In a comparatively dry atmosphere, sodium burns quietly, giving off a dense white caustic smoke, which can cause choking and coughing.

Happy almost Halloween! :)

Answer:

CHO

Explanation:

Carbon = 41%,  Hydrogen = 4.58%, oxygen = 54.6%

Step 1:

Divide through by their respective relative atomic masses

41/ 12,         4.58/1,         54.6/16

3.41              4.58            3.41

Step 2:

Divide by the lowest ratio:

3.41/3.41,      4.58/3.41,     3.41/3.41

1,                    1,                  1

Hence the empirical formula is CHO

Answer:

The empirical formula of X is C3H4O3.

Explanation:

Answer:

15.2mL of the 0.10M sodium formate solution and 4.8mL of the 0.10M formic acid solution.

Explanation:

To find the pH of a buffer based on the concentration of the acid and conjugate base we must use Henderson-Hasselbalch equation:

pH = pKa + log [A⁻] / [HA]

Where [A⁻] could be taken as moles of the sodium formate and [HA] moles of the formic acid

4.25 = 3.75 + log [A⁻] / [HA]

0.5 = log [A⁻] / [HA]

3.162 = [A⁻] / [HA] (1)

As both solutions are 0.10M and you want to create 20mL of the buffer, the moles are:

0.10M  * 20x10⁻³L =

2x10⁻³moles = [A⁻] + [HA] (2)

Replacing (2) in (1):

3.162 = 2x10⁻³moles - [HA] / [HA]

3.162 [HA] = 2x10⁻³moles - [HA]

4.162[HA] = 2x10⁻³moles

[HA] = 4.805x10⁻⁴ moles

[A⁻] = 2x10⁻³moles - 4.805x10⁻⁴ moles = 1.5195x10⁻³moles

That means, to create the buffer you must add:

[A⁻] = 1.5195x10⁻³moles * (1L / 0.10mol) = 0.0152L =

[HA] = 4.805x10⁻⁴ moles * (1L / 0.10mol) = 0.0048L =

Answer:

ARSENIC

Explanation:

It has an atomic number of 33

Moles of [tex]H_2O[/tex] ,

[tex]n_{H_2O}=\dfrac{42}{2\times 1 + 16}=\dfrac{42}{18}\\\\n_{H_2O}=2.33\ moles[/tex]

Moles of acetic acid [tex]HCH_3CO_2[/tex] ,

[tex]n_{A.A}=\dfrac{77}{1 + 12 + 3 + 12 + 16\times 2}=\dfrac{77}{60}\\\\n_{A.A}=1.28\ moles[/tex]

Mole fraction of water :

[tex]M.F_{H_2O}=\dfrac{n_{H_2O}}{n_{H_2O}+n_{A.A}}\\\\M.F_{H_2O}=\dfrac{2.33}{2.33+1.28}\\\\M.F_{H_2O}=0.645[/tex]

Therefore, mole fraction of water in this solution is 0.645 .

Hence, this is the required solution.

Answer:

D

Explanation:

Identifying unique features of evidence

A laboratory is a place where scientific investigations and experiments are conducted. Observing a phenomenon in the lab includes identifying unique features of evidence. Thus, option D is correct.

An observation is said to be the deduction that is seen or heard and is due to the actions of the process or event that are gained from the information from a conducted experiment.

It is an important factor in an experiment and research and is used in the lab to falsify or prove the hypothesis. It is made based on the experimental setup and involves various steps.

The observations are used to draw conclusions and inferences based on the detailed identification of the characteristics of the evidence. The evidence supports the observation.

Therefore, option D. the features of evidence are the correct option.

Learn more about observations here:

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Answer:

A) enthalpy of reaction

Explanation:

The region C signifies the enthalpy of reaction.

This diagram is the energy profile of an endothermic reaction. In such reaction, heat is absorbed from the surrounding. At the end of the reaction, the heat of product is lesser than that of the reactants.

it is indeed A) enthalpy of reaction

Answer:

3.13%.

Explanation:

The following data were obtained from the question:

Original amount (N₀) = 0.15

Half life (t½) = 2 mins

Number of half-life (n) = 5

Fraction of sample remaining =.?

Next, we shall determine the amount remaining (N) after 5 half-life. This can be obtained as follow:

Amount remaining (N) = 1/2ⁿ × original amount (N₀)

NOTE: n is the number of half-life.

N = 1/2ⁿ × N₀

N = 1/2⁵ × 0.15

N = 1/32 × 0.15

N = 0.15/32

N = 4.69×10¯³

Therefore, 4.69×10¯³ is remaining after 5 half-life.

Finally, we shall the fraction of the sample remaining after 5 half-life as follow:

Original amount (N₀) = 0.15

Amount remaining (N) = 4.69×10¯³

Fraction remaining = N/N₀ × 100

Fraction remaining = 4.69×10¯³/0.15 × 100

Fraction remaining = 3.13%

Answer:..

Explanation:

Answer:

1) 97.6%

2) No the purity is not acceptable because the standard is 99.5% purity.

3) Yes I will repeat the titration experiment to confirm my result.

Explanation:

Equation of the reaction;

C7H6O2(aq) + NaOH(aq) ---------> C7H5ONa(aq) + H2O(aq)

From the information provided;

Number of moles of NaOH reacted = concentration × volume = 20.15/1000 × 0.500 = 0.01 moles

From the reaction equation;

1 mole of C7H6O2 reacts with 1 mole of NaOH

Hence 0.01 moles of C7H6O2 will react with 0.01 moles of NaOH

Mass of C7H6O2 reacted = number of moles of C7H6O2 × molar mass of C7H6O2

Molar mass of C7H6O2 = 122.12 g/mol

Mass of C7H6O2 reacted = 0.01 moles × 122.12 g/mol = 1.22 g

Percentage by mass of pure C7H6O2 in the impure sample = 1.22/1.250 × 100 = 97.6 %

Answer:

[H+] = 7.576x10⁻⁴M

pH = 3.12

Explanation:

Based on the equilibrium of the nicotinic acid in water:

HC6H4NO2(aq) + H2O(l) ⇄ C6H4NO2-(aq) + H3O+(aq)

Ka = [C6H4NO2-] [H3O+] / [HC6H4NO2]

As both C6H4NO2-(aq) and H3O+(aq) comes from the same equilibrium, we can approximate their concentration as X and replace:

Ka = [C6H4NO2-] [H3O+] / [HC6H4NO2]

1.4x10⁻⁵ = [X] [X] / [0.041M]

5.47x10⁻⁷ = X²

And as pH is defined as -log [H⁺]

Answer:

make an observation that describes a problem

Explanation:

Answer:

The first step in the Scientific Method is to make objective observations.

Explanation:

....-

Answer:

Explanation:

Iodine is the most flexible of the atoms in Group 17 of the periodic table. It can have more than 1 charge, especially when combined with oxygen. The answer that you are expected to give, I think is C. Iodine's dominant charge is - 1

Answer:

The energy of each transition is approximately [tex]1.98\times 10^{-19}\; \rm J[/tex].

The frequency of photons released in such transitions is approximately [tex]3.00\times 10^{14}\; \rm Hz[/tex].

Explanation:

The Rydberg Equation gives the wavelength (in vacuum) of photons released when the electron of a hydrogen atom transitions from one main energy level to a lower one.

The Rydberg Equation gives the following relation:

[tex]\displaystyle \frac{1}{\lambda_\text{vac}} = R_\text{H} \cdot \left(\frac{1}{{n_2}^2}} -\frac{1}{{n_1}^2}\right)[/tex].

Rearrange to obtain and expression for [tex]\lambda_\text{vac}[/tex]:

[tex]\displaystyle \lambda_\text{vac} = \frac{1}{\displaystyle R_\text{H}\cdot \left(\frac{1}{{n_2}^2} - \frac{1}{{n_1}^2}\right)}[/tex].

In this question, [tex]n_1 = 7[/tex] while [tex]n_2 = 3[/tex]. Therefore:

[tex]\begin{aligned} \lambda_\text{vac} &= \frac{1}{\displaystyle R_\text{H}\cdot \left(\frac{1}{{n_2}^2} - \frac{1}{{n_1}^2}\right)} \\ &\approx \frac{1}{\displaystyle 1.09678 \times 10^{7}\; \rm m^{-1} \cdot \left(\frac{1}{3^2} - \frac{1}{7^2}\right)} \approx 1.0 \times 10^{-6}\; \rm m \end{aligned}[/tex].

Note, that [tex]1.0\times 10^{-6}\; \rm m[/tex] is equivalent to [tex]1000\; \rm nm[/tex]. That is: [tex]1.0\times 10^{-6}\; \rm m = 1000\; \rm nm[/tex].

Look up the speed of light in vacuum: [tex]c \approx 3.00\times 10^{8}\; \rm m \cdot s^{-1}[/tex]. Calculate the frequency of this photon:

[tex]\begin{aligned} f &= \frac{c}{\lambda_\text{vac}} \\ &\approx \frac{3.00\times 10^{8}\; \rm m\cdot s^{-1}}{1.0\times 10^{-6}\; \rm m} \approx 3.00 \times 10^{14}\; \rm Hz\end{aligned}[/tex].

Let [tex]h[/tex] represent Planck constant. The energy of a photon of wavelength [tex]f[/tex] would be [tex]E = h \cdot f[/tex].

Look up the Planck constant: [tex]h \approx 6.62607 \times 10^{-34}\; \rm J \cdot s[/tex]. With a frequency of [tex]3.00\times 10^{14}\; \rm Hz[/tex] ([tex]1\; \rm Hz = 1\; \rm s^{-1}[/tex],) the energy of each photon released in this transition would be:

[tex]\begin{aligned}E &= h \cdot f \\ &\approx 6.62607 \times 10^{-34}\; \rm J\cdot s^{-1} \times 3.00 \times 10^{14}\; \rm s^{-1} \\ &\approx 1.98 \times 10^{-19}\; \rm J\end{aligned}[/tex].

The energy of the transition between n = 7 and n = 3  is 1.96 × 10^-19 J while the frequency is 3 × 10^14 Hz.

Using the Rydberg Equation for energy;

ΔE = -RH(1/n^2final - 1/n^2initial)

Given that;

nfinal = 3

ninitial = 7

RH = 2.18 × 10^-18 J

ΔE = - 2.18 × 10^-18(1/3^2 - 1/7^2)

ΔE = - 2.18 × 10^-18(0.11 - 0.02)

ΔE = - 1.96 × 10^-19 J

For the second part;

Since the wavelength is 1000nm, we have;

λ = 1000nm

c = 3 × 10^8 m/s

f = ?

c = λf

f = c/λ

f = 3 × 10^8 m/s/1000 × 10^-9 m

f = 3 × 10^8 m/s/ 1 × 10^-6 m

f = 3 × 10^14 Hz

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Answer:

4.22mL

Explanation:

V=m/d

v= 18.45g/4.37g/mL

Answer:

the answer is B

Explanation:

When an atom has an equal number of electrons and protons, it has an equal number of negative electric charges

Answer:

3

Explanation:

I wish you the best, its three or 2

Answer:

2

Explanation:

Edge 2021

Answer:

100 joules​

Explanation:

The mechanical energy (M.E) of an object describes the objects ability to do work. The mechanical energy encompasses the object's energy due to its position (potential energy) and its energy due to motion (kinetic energy).

Therefore,

M.E = K.E + P.E

According to this question, potential energy (P.E) of the roller coaster is 50J and the kinetic energy (K.E) is also 50J. Hence, the mechanical energy (M.E) is

M.E = 50J + 50J

M.E = 100J

If the P.E and K.E of a roller coaster is 50 Joules respectively, the mechanical energy of the roller coaster is 100 Joules.

Given the following data:

To find the mechanical energy of the roller coaster:

The mechanical energy of a physical object or body is the total sum of the potential energy (P.E) and kinetic energy (K.E) possessed by an object.

Mathematically, mechanical energy is given by the formula;

Substituting the given parameters into the formula, we have;

[tex]M.E = 50 + 50[/tex]

Mechanical energy (M.E) = 100 Joules.

Therefore, the mechanical energy of the roller coaster is 100 Joules.

Read more: https://brainly.com/question/23153766

Answer:

Explanation:

Out of aspirin, acetaminophen and caffeine, aspirin is an acid because it is acetyl saliciylic acid . Hence it can be tested with litmus paper .

acetaminophen contains phenolic functional group , hence it is a weak acid . It can be tested with any test with which phenol test are done,  like with neutral solution of ferric chloride .

caffeine is weak basic substance . It can also be tested with the help of testing a basic substance .

Answer:

Changes in environment, food source changes and disease?

Explanation:

I dont know what the answer choices are

Answer:

changes in the environment

Explanation:

like digging big holes.

Hope this helps!

Answer:

C.

Explanation:

You can use the series of elimination for this. First, you look at A. Technology is not an understanding of something new, so we cross that out. Second, you look at B. Technology isn't a series of steps, so we can mark that one off. Third, you look at C. Technology is something created using science for use by society, so we can keep that in mind. Lastly, we check D. Technology doesn't match up to the definition, so we can cross that one out. The answer that would make the most sense would be D.

Answer:

Final volume  = 0.44 L

Explanation:

Given data:

Initial volume of balloon = 1.1 L

Initial pressure = 0.80 atm

Final volume = ?

Final pressure = 2.0 atm

Solution:

The given problem will be solved through the Boly's law,

"The volume of given amount of gas is inversely proportional to its pressure by keeping the temperature and number of moles constant"

Mathematical expression:

P₁V₁ = P₂V₂

P₁ = Initial pressure

V₁ = initial volume

P₂ = final pressure

V₂ = final volume  

Now we will put the values in formula,

P₁V₁ = P₂V₂

0.80 atm × 1.1 L = 2.0 atm × V₂

V₂ = 0.88 atm. L/ 2.0 atm

V₂ = 0.44 L

Answer:

2,2,3- trimethylhexane because it has more carbon atoms than pentane.

Explanation:

Hello.

In this case, since the physical properties of organic compounds are intensified as the number of carbon atoms start increasing on it, the larger the amount of carbon atom, the higher the boiling point since more energy is required to allow the liquid-phase molecules to transcend to the vapor-phase.

In such a way, since pentane has five carbon atoms and 2,2,3- trimethylhexane has nine carbon atoms, 2,2,3- trimethylhexane has the highest boiling point.

Best regards.

Answer:

1.14 M

Explanation:

Let's consider the following reaction.

butane ⇄ isobutane

We can use the concentrations at equilibrium to calculate the equilibrium constant.

Kc = [isobutane] / [butane]

Kc = 2.5 / 1.0

Kc = 2.5

If we add 0.50 M of isobutane, we get [isobutane] = 2.5 + 0.50 = 3.0 M.

This will be an initial concentration in an ICE chart.

        butane ⇄ isobutane

I           1.0              3.0

C         +x                -x

E        1.0+x           3.0-x

The equilibrium constant is:

Kc = 2.5 = [isobutane] / [butane]

2.5 = (3.0-x) / (1.0+x)

2.5 + 2.5x = 3.0-x

x = 0.14

The equilibrium concentration of butane is:

[butane] = 1.0+x = 1.14 M

C – 19,9%, H – 2,2%, N – 11,6%, O – x%

[tex]M=120\frac{g}{mol}[/tex]

1 percentage

The entire molecule is 100% and all the components of the compound add up to 100%.

100% - 19,9% - 2,5% - 11,6% = 66,1%

The compound contains 66,1% oxygen.

2 molar masses

[tex]M_{C}=12,01\frac{g}{mol}[/tex]

[tex]M_{H}=1,008\frac{g}{mol}[/tex]

[tex]M_{O}=15,999\frac{g}{mol}[/tex]

[tex]M_{N}=14,007\frac{g}{mol}[/tex]

3 masses

The compound has a molar mass of 120g/mol. So one molecule weighs 120 g. To find out how much the percentage of a component weighs, you have to calculate it using the molar mass.

carbon

19,8% of 120g

[tex]m=120g*0,198\\m=23,76g[/tex]

One molecule contains 23,76g of carbon.

hydrogen

2,5% of 120g

[tex]m=120g*0,025\\m=3g[/tex]

One molecule contains 3g of hydrogen.

oxygen

66,1% of 120g

[tex]m=120g*0,661\\m=79,32g[/tex]

One molecule contains 79,32g of oxygen.

nitrogen

11,6% of 120g

[tex]m=120g*0,0,116\\m=13,92g[/tex]

One molecule contains 13,92g of nitrogen.

4 amount of substance

carbon

[tex]n=\frac{23,76g}{12,01\frac{g}{mol} }\\n=1,98mol[/tex]

The compound contains about 2 moles of carbon.

hydrogen

[tex]n=\frac{3g}{1\frac{g}{mol} }\\n=3mol[/tex]

The compound contains about 3 moles of hydrogen.

oxygen

[tex]n=\frac{79,32g}{15,999\frac{g}{mol} }\\n=4,96mol[/tex]

The compound contains about 5 moles of oxygen.

nitrogen

[tex]n=\frac{13,92g}{14,007\frac{g}{mol} }\\n=0,99mol[/tex]

The compound contains about 1 moles of nitrogen.

5. molecular formula

The formula results from the ratio of the amounts of substance.

[tex]n_{C} :n_{H} :n_{O} :n_{N} =2:3:5:1\\C_{2}H_{3}NO_{5}[/tex]

The molecular formula of the given compound is C₂H₃NO₅, and percent composition of oxygen in it is 66.1%.

Mass of any composition of any compound will be calculated by using the below formula as:

Mass of component = (% composition)×(mass of compound) / 100

Given mass of compound = 120g/mol

Total composition of compound (100%) = Percent composition of all components

% composition of oxygen = 100 - (19.8 + 2.50 + 11.6) = 66.1%

Moles will be calculated as:

n = W/M, where

W = given mass

M = molar mass

Mass of Carbon component = (0.198)(120g) = 23.76g

Moles of Carbon atom = 23.76g / 12.01g/mol = 1.98mol = 2 moles

Mass of Nitrogen component = (0.116)(120g) = 13.92g

Moles of Nitrogen atom = 13.92g / 14.007g/mol = 0.99mol = 1 moles

Mass of Oxygen component = (0.661)(120g) = 79.32g

Moles of Oxygen atom = 79.32g / 15.99g/mol = 4.96mol = 5 moles

Mass of Hydrogen component = (0.025)(120g) = 3g

Moles of Hydrogen atom = 3g / 1g/mol = 3 moles

So, the molecular formula of the compound on the basis of moles of given entities is C₂H₃NO₅.

Hence required molecular formula is C₂H₃NO₅.

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Answer:

Explanation:

NaNO₃  = Na⁺  + NO₃⁻¹

.497 M                 .497 M

moles of NO₃⁻¹ = .897 x .497 = .4458 moles

Ca( NO₃)₂  = Ca + 2 NO₃⁻¹

.341 M                    2 x .341 M = .682 M

moles of NO₃⁻¹ = .813 x .682 = .5544 moles

Total moles =  .4458 moles  +  .5544 moles

= 1.0002 moles

volume of solution = 897 + 813 = 1710 mL

= 1.710 L

concentration of nitrate ion = 1.0002 / 1.710 M

= .585 M

Answer:

The answer is actually 3. The disorder of a system.