What is the name for the distance that light travels in 365 days?

Which of the following materials is useful for making molds because it has a low melting point?

inessss [21]

Molds are created to achieve a specific design of a material. These materials either came from a process of having a higher or lower temperature. Therefore, the molder must have thermal resistant properties. Low melting points means that the material to be shaped came from a cooler process. Wood and metal have higher thermal conductivity and therefore can easily be cooled. The wax can turn really hard and can be unbreakable when present in colder materials due to the lipids present in it. Clay however can become a mold because of its low melting point.

7 0

3 years ago

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Kidneys help regulate the concentration of which substance in the blood?

krek1111 [17]

Bicarbonate, sodium, potassium
are regulated by the kidneys.

3 0

3 years ago

A polymer P is made up of two monodisperse fractions; fraction A with molecular weight of 1000 g/mole and fraction B with a mole

vesna_86 [32]

Answer:

a)Number average molecular weight is 50, 500 g/mol

b) Weight average molecular weight is 99, 019.8 g/mol

Explanation:

We have a polymer P made up of two monodisperse fractions.

A with molecular weight of MA = 1000 g/mol and B with MB =100000 g/mol.

The batch contains an equal mole fraction of each component A and B.

Let's suppose a total number (Nt) of mols 2 moles. Equal fraction means XA = 0.5 and XB =0.5

Nt = 2 mol

Na = 2*0.5 = 1 mol

Nb = 2*0.5 = 1 mol.

So, we have 1 mol of A, 1 mol of B and 2 moles in total.

a) The number average molecular weight (NAM) is calculate using the mole numbers of each component. In this case, we will multiple each component molecular weight by the number of moles of each one. After that we will sum them and finally to divide by the total number of moles.

NAM = (Na*MA + Nb*MB)/(Nt)

NAM = (1 mol *1000 g/mol + 1*100000 g/mol ) /(2 mol)

NAM = 50500 g/mol

The number average molecular weight for the polymer P is 50,500 g/mol

b) Weight average molecular weight (WAM) is calculated using the mass quantities of each component. Weight mass of A (WA), weight mass of B (WB) are calculate using the moles of A, B and their molecular weights respectively. Total Weight (WT)

WA = Na*MA = 1 mol *1000 g/mol = 1000 g A

WB = Nb*MB = 1mol * 100000 g/mol = 100 000 gB

WT = WA + WB = 101 000 g

Now we will calculate average molecular using weights, we will multiple each component molecular weight by the mass of each one. After that we will sum them and finally to divide by the total mass.

WAM = (WA*MA + WB*MB)/(WT)

WAM = (1000 g *1000 g/mol + 100000 g*100000 g/mol )/(101 000 g)

WAM = 99 019.8 g/mol

The weight average molecular weight for polymer P is 99, 019.8 g/mol

6 0

4 years ago

A student is given 2.19 g of an unknown acid, which can be either oxalic acid, H2C2O4, or citric acid, H3C6H5O7. To determine wh

Alina [70]

Answer:

The unknown acid is citric acid.

There is 0.0342 moles of NaOH consumed.

Explanation:

Step 1: Data given

Mass of the unknown acid = 2.19 gram

Titrating with 0.560 M of NaOH

The equivalence point is reached when 61.0 mL are added

Molar mass of oxalic acid = 90.03 g/mol

Molar mass of citric acid = 192.12 g/mol

Step 2: The balanced equations for both acids

The reaction between oxalic acid and NaOH is:

H2C2O4 + 2NaOH → Na2C2O4 + 2H2O

The reaction between citric acid and NaOH is:

H3C6H5O7 +3NaOH → Na3C6H5O7 + 3 H2O

Step 3: Calculate the number of moles of the acid

Moles = mass / Molar mass

In case of oxalic acid: 2.19 grams / 90.03 g/mol = 0.0243 moles

In case of citric acid: 2.19 grams /192.12 g/mol = 0.0114 moles

Step 4: Calculate number of moles of NaOH

The mole of NaOH required for titration;

number of moles = Molar mass * volume = (0.560 M * 0.061 L) = 0.03416 mol

Step 5: Calculate which acid

For each mole of oxalic 2 moles of NaOH is required, for 0.0243 mol citric acid 0.0243 *2= 0.0486 mol NaOH is required. This is more than the number of moles consumed.

For each mole of citric acid 3 moles of NaOH is required, for 0.0114 mol citric acid 0.0114 * 3= 0.0342 mol NaOH is required. This is the number of moles NaOH used for the titration.

The unknown acid is citric acid. There is 0.0342 moles of NaOH consumed.

8 0

3 years ago

Which pairing below does not correctly match the scientist with the contribution to the understanding of the atom? A. Proust and

Lyrx [107]

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.

5 0

4 years ago

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