_____ Na3PO4 + _____ KOH arrow _____ NaOH + ___________K3PO4 <br> How do I balance this equation?

A 4.36-g sample of an unknown alkali metal hydroxide is dissolved in 100.0 mL of water. An acid-base indicator is added, and the

BARSIC [14]

Answer:

Rb+

Explanation:

Since they are telling us that the equivalence point was reached after 17.0 mL of 2.5 M HCl were added , we can calculate the number of moles of HCl which neutralized our unknown hydroxide.

Now all the choices for the metal cation are monovalent, therefore the general formula for our unknown is XOH and we know the reaction is 1 equivalent acid to 1 equivalent base. Thus we have the number of moles, n, of XOH and from the relation n = M/MW we can calculate the molecular weight of XOH.

Thus our calculations are:

V = 17.0 mL x 1 L / 1000 mL = 0.017 L

2.5 M HCl x 0.017 L = 2.5 mol/ L x 0.017 L = 0.0425 mol

0.0425 mol = 4.36 g/ MW XOH

MW of XOH = (atomic weight of X + 16 + 1)

so solving the above equation we get:

0.0425 = 4.36 / (X + 17 )

0.7225 +0.0425X = 4.36

0.0425X = 4.36 -0.7225 = 3.6375

X = 3.6375/0.0425 = 85.59

The unknown alkali is Rb which has an atomic weight of 85.47 g/mol

6 0

3 years ago

Name the separation technique which could be used to separate mud and water without heating

Westkost [7]

Answer:

Decantation

Explanation:

Decantation is a process to separate

mixtures by removing a liquid layer that

is free of a precipitate, or the solids

deposited from a solution. The purpose

may be to obtain a decant (liquid free

from particulates) or to recover the

precipitate.

Decantation relies on gravity to pull

precipitate out of the solution, so there is

always some loss of product, either from

the precipitate not fully falling out of the

solution or from liquid remaining when

separating it from the solid portion.

The Decanter

A piece of glassware called a decanter is

used to perform decantation. There are

several decanter designs. A simple

version is a wine decanter, which has a

wide body and a narrow neck. When

wine is poured, solids stay in the base of

the decanter.

In the case of wine, the solid is usually

potassium bitartrate crystals. For

chemistry separations, a decanter may

have a stopcock or valve to drain the

precipitate or dense liquid, or it may

have a partition to separate fractions.

Use of Alum and filtration process can also be administered for further purification

8 0

3 years ago

A piece of metal with a mass of 142 g is placed in a 50 mL graduated cylinder. The water level rises from 20 mL to 40 mL. What i

zheka24 [161]

Explanation:

The end goal of this question is to find density. Density can be found using the following formula:

D=m/v

D=Density

m=mass

v=volume

Therefore we need mass and volume to find density. Mass is already given in the question as 142g. All we have left is volume. When a solid is placed in water in a graduated cylinder the volume goes up. This means if you subtract the volume after the metal was placed from before it was placed, you can find the volume of the metal. Therefore the volume of the metal is 40mL-20mL=20mL. However typically, volume is found in liters so the volume should be .04L-.02L=0.02L. Now that we have volume and mass we can find density using the formula d=m/v. So 142/.02=7,100 grams per liget or 7.1 kilograms per liter. This answer seems unrealistic so I would double check with your teacher about the question.

Hope I helped, 2Trash4U

5 0

3 years ago

Which of these statements about atomic models is most likely correct?

taurus [48]

Answer:

The correct option is the second option

Explanation:

Generally, the aim of science is to understand a particular concept in the best and the most correct way possible; hence experiments are done and repeated to ensure an explanation is actually true about a concept or need modification.

The atomic models have also been a "beneficiary" of this process. The different atomic models are usually been improved upon as scientists leaned more. For example, the Dalton's atomic theory has been modified to a more correct atomic description; some of which are shown below

(1) Dalton's theory suggested that an atom is the smallest unit of a molecule. We know now from different experiments (by J. J Thompson and Rutherford) that atoms are not the smallest molecules and are made up of smaller particles known as protons, neutrons and electrons.

(2) Dalton's theory suggested that atoms of the same elements are alike in all aspects. The knowledge of isotopy shows this is not always the case. As atoms of the same elements (isotopes) have the same atomic number but different mass number; hence cannot be said to be the same in all aspects.

(3) Dalton's theory also suggested that when atoms react, they do so in fixed, simple whole number ratio. The knowledge of organic chemistry shows atoms do not always react in simple whole number ratios

There are several modifications to different postulations by scientists that have also occurred aside from this, hence the most correct answer is that "As scientists learned more, they modified the atomic model"

5 0

3 years ago

A student took a calibrated 250.0 gram mass, weighed it on a laboratory balance, and found it read 266.5 g. What was the student

marta [7]

Answer:

$\boxed{\text{6.60 \%}}$

Explanation:

$\text{Percent error} = \dfrac{\lvert \text{Measured - Actual}\lvert}{ \text{Actual}} \times100 \,\%$

$\text{\% error} = \dfrac{\lvert 266.5 - 250.0\lvert}{250.0} \times 100 \, \% = \dfrac{\lvert 16.5\lvert}{250.0} \times 100 \, \% = \dfrac{16.5}{250.0} \times 100 \,\%\\\\ = 0.0660 \times 100 \, \% = \textbf{6.60 \%}\\\text{The student's percent error is $\boxed{\textbf{6.60 \%}}$}$

4 0

3 years ago

_____ Na3PO4 + _____ KOH arrow _____ NaOH + ___________K3PO4 How do I balance this equation?

___ Na3PO4 + _ KOH arrow _ NaOH + _________K3PO4 How do I balance this equation?