PLEASE HELP!!! 25 POINTS! Phosphoric acid reacts with sodium hydroxide: H3PO4(aq) + 3NaOH(aq) ---> Na3PO4(aq) + 3H2O(l)If 7.50 mol H3PO4 is made to react with 15.0 mol NaOH, identify the limiting reagent. Show all work!


Answer 1


Sodium hydroxide (NaOH) is the limiting reactant


Step 1: Data given

Number of moles of NaOH = 15.0 mol

Number of moles of H3PO4 = 7.50 mol

Molar mass of NaOH = 40 g/mol

Molar mass of H3PO4 = 98 g/mol

Step 2: The balanced equation:

H3PO4(aq) + 3NaOH(aq) → Na3PO4(aq) + 3H2O(l)

Step 3: Calculate the limiting reactant

For 1 mole of H3PO4, we need 3 moles of NaOH

NaOH is the limiting reactant. It will completely be consumed. (15 moles)

H3PO4 is in excess, there will react 15.0 / 3 = 5 moles

There will remain 7.5 - 5.0 = 2.5 moles

There will be produced 15.0/3 = 5.0 moles of Na3PO4

There will be produced 15.0 moles of H2O

Sodium hydroxide (NaOH) is the limiting reactant

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Wich of thses is an example of an environment changing slowly? a. hurricane
b. tsunami
c.pomd succession
d. flooding


C because the othern ones happen suddenly while succession is slower
I think It's letter A

Compare and contrast an electric generator and a battery??


Both generators and batteries both convert a form of energy into electrical energy. In a battery, a chemical reaction takes place which converts chemical energy into electrical energy. In a generator however, many times mechanical energy is being converted into electrical energy. A process called electromagnetic induction can take place in some generator which is where an electromagnet is used to help conduct electricity. hope this helped!!! 

Calculation of Original pH from Final pH after Titration A biochemist has 100 mL of a 0.10 M solution of a weak acid with a pKa of 6.3. She adds 6.0 mL of 1.0 M HCl, which changes the pH to 5.7. What was the pH of the original solution?





A weak acid dissociates in an equilibrium reaction, thus, it is in equilibrium with its conjugate base:

HA ⇄ H⁺ + A⁻

The equilibrium constant (Ka) can be calculated, where Ka = [H⁺]*[A⁻]/[HA]. Using the -log form, we can also have pKa = -logKa. By the Handerson-Halsebach (HH) equation, the relation between pH and pKa is:

pH = pKa + log[A⁻]/[HA]

So, when pH = 5.7, for this acid, the ratio of [acid]/[base] ([HA]/[A-]) is:

5.7 = 6.3 + log[A⁻]/[HA]

log[A⁻]/[HA] = -0.6

log[HA]/[A⁻] = 0.6

[HA]/[A⁻] =

[HA]/[A⁻] = 3.98 = 4.0

If the ratio of acid and base is 4 to 1, it means that 80%(4/5) of the acid is protonated after the addition of the HCl.

The initial number of moles of the weak acid was: 100 mL * 0.10 M = 10 mmol, so after the addition of HCl, 8 mmol is in the acid form (80% of 10). It was added 6.0 mmol of HCl (6.0 mL*1.0M). Thus, 6.0 mmol of H+ was added and reacted with the conjugate base of the weak acid.

For the mass conservation, the initial amount of the protonated weak acid must be 2.0 mmol (8 - 6), and the number of moles of the conjugate base was 8.0 mmol. Using the HH equation:

pH = 6.3 + log(8/2)

pH = 6.3 + 0.6

pH = 6.9


The solubility product for an insoluble salt with the formula mx3 is written as __________, where s is the molar solubility.


The solubility product would be written as follows:

Ksp = [M][3X]^3

letting s as the molar solubility

Ksp = s(3s)^3
Ksp = s(27s^3)
Ksp = 27s^4

The solubility product is a mathematical product of the dissociated ion concentration in the solution and raised to the power of the stoichiometric coefficients. Hope this helps.

Energy from the Sun arrives at the top of the Earth's atmosphere with an intensity of 1.1 kW/m2 . How long does it take for 1.91×109 J to arrive on an area of 1 m2 ?



1.736 × 10⁶


Data provided in the question:

Intensity of the energy received from the sun = 1.1 kW/m² = 1.1 × 10³ W/m²

Energy  required to arrive = 1.91 × 10⁹ J

Area at the surface = 1 m²


we know that

Energy = Intensity × Area × Time


1.91 × 10⁹ = ( 1.1 × 10³ ) × 1 × Time


Time = [ 1.91 × 10⁹ ] ÷ [ 1.1 × 10³ ]


Time = 1.736 × 10⁶


At what time should we definitely seek shade to avoid sun exposure? A:Between 6 a.m. and 8 a.m.
B:Between 8 a.m. and 10 a.m.
C:Between 10 a.m. and 4 p.m.
D:Between 4 p.m. and 10 p.m.
Couldn't find Science in the "Pick a subject" box ;-;


C between 10 and 4.

We should definitely seek shade to sun exposure between 10 A.M. and 4 P.M.

Hope this helped!


The following data is given to you about a reaction you are studying: Overall reaction: 2A  D Proposed mechanism: Step 1 A + B  C (slow) Step 2 C + A  D + B (fast) [A]o = 0.500 M [B]o = 0.0500 M [C]o = 0.500 M [D]o = 1.50 M This reaction was run at a series of temperatures and it was found that a plot of ln(k) vs 1/T (K) gives a straight line with a slope of -982.7 and a Y intercept of -0.0726. What is the initial rate of the reaction at 298K?


Answer : The initial rate of the reaction at 298 K is,

Explanation :

The Arrhenius equation is written as:

Taking logarithm on both the sides, we get:



k = rate constant

Ea = activation energy

T = temperature

R = gas constant  = 8.314 J/K.mole

A = pre-exponential factor

The equation (1) is of the form of, y = mx + c i.e, the equation of a straight line.

Thus, if we plot a graph of vs then the graph shows a straight line with negative slope. That means,

Slope of the line =


Intercept =

As we are given that:

Slope of the line = -982.7 =

Intercept = -0.0726 =

Now we have to calculate the value of rate constant by putting the value of slope, intercept and temperature (298K) in equation 1, we get:

The value of rate constant is,

Now we have to calculate the initial rate of the reaction at 298 K.

As we know that the slow step is the rate determining step. So,

The slow step reaction is,

The expression of rate law for this reaction will be,

As we are given that:

[A] = 0.500 M

[B] = 0.0500 M

k =

Now put all the given values in the rate law expression, we get:

Therefore, the initial rate of the reaction at 298 K is,


A team of researchers are working on a project to make a new kind of airplane fuel. During their experiment, there was an explosion that destroyed the lab. While they were cleaning up the debris, they discovered a number of pieces of frozen metal. The scientific community was amazed. The researchers were so excited to report that they had discovered a fuel that burns so hot that it becomes cold. They were not sure of the true importance of their discovery but they knew it was something that had never been seen before. The researchers quickly wrote up a report, created a press release, and applied for a patent. The news spread quickly through the world wide scientific community and soon other scientists were trying to replicate their experiment. Much to the relief of the original team or researchers, no other scientist could ever replicate their find. Would this example be considered science or pseudoscience? Why or Why not?


Well for a start, this makes absolutely no sense, "discovered a fuel that burns so hot that it becomes cold." 

And yes, it's not science if the experiment can't be repeated. In fact they should WANT it to be repeated so that you can get credit for discovering something new and then possibly harness this effect to produce useful applications. 

For all we know they had a fewer of LN2 in the lab that got shredded by the blast, LN2 could certainly have frozen many things (not metal though, since metal is already solid at room temperature, (except for mercury)), and afterwards would leave no trace.

Ions that are present before and after a neutralization reaction are



spectator ions


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