Student mixes 5 g of sand into a beaker of 20 g of water. Is this a physical or chemical change-why?

An experiment shows that a 236 mL gas sample has a mass of 0.443 g at a pressure of 740 mmHg and a temperature of 22 ∘C. What is

aleksley [76]

Answer:

49.2 g/mol

Explanation:

Let's first take account of what we have and convert them into the correct units.

Volume= 236 mL x ( $\frac{1 L}{1000 mL}$ ) = .236 L

Pressure= 740 mm Hg x ( $\frac{1 atm}{760 mm Hg}$ )= 0.97 atm

Temperature= 22C + 273= 295 K

mass= 0.443 g

Molar mass is in grams per mole, or MM= $\frac{mass}{moles}$ or MM= $\frac{m}{n}$ . They're all the same.

We have mass (0.443 g) we just need moles. We can find moles with the ideal gas constant PV=nRT. We want to solve for n, so we'll rearrange it to be

n= $\frac{PV}{RT}$ , where R (constant)= 0.082 L atm mol-1 K-1

Let's plug in what we know.

n= $\frac{(0.97 atm)(0.236 L)}{(0.082)(295K)}$

n= 0.009 mol

Let's look back at MM= $\frac{m}{n}$ and plug in what we know.

MM= $\frac{0.443 g}{0.009 mol}$

MM= 49.2 g/mol

3 0

2 years ago

Which ion does not have a noble gas configuration in its ground state?

goldfiish [28.3K]

I think the answer would be Ga3+

3 0

3 years ago

Harry Hess resurrected Wegener’s continental drift hypothesis and also the mantle convection idea of Holmes.

stepan [7]

Answer:

true

Explanation:

7 0

2 years ago

Read 2 more answers

Hydrogen fluoride is used in the manufacture of Freons (which destroy ozone in the stratosphere) and in the production of alumin

Lerok [7]

<u>Answer:</u> The percentage yield of HF is 73.36 %

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ ....(1)

For calcium fluoride:

Given mass of calcium fluoride = 6.25 kg = 6250 g (Conversion factor: 1 kg = 1000 g)

Molar mass of calcium fluoride = 78.07 g/mol

Putting values in above equation, we get:

$\text{Moles of calcium fluoride}=\frac{6250g}{78.07g/mol}=80.05mol$

For the given chemical reaction:

$CaF_2+H_2SO_4\rightarrow CaSO_4+2HF$

By Stoichiometry of the reaction:

1 mole of calcium fluoride produces 2 moles of hydrofluoric acid

So, 80.05 moles of calcium fluoride will produce = $\frac{2}{1}\times 80.05=160.1mol$ of hydrofluoric acid

Now, calculating the theoretical yield of hydrofluoric acid using equation 1, we get:

Moles of of hydrofluoric acid = 160.1 moles

Molar mass of hydrofluoric acid = 20.01 g/mol

Putting values in equation 1, we get:

$160.1mol=\frac{\text{Theoretical yield of hydrofluoric acid}}{20.01g/mol}=3203.6g=3.20kg$

To calculate the percentage yield of hydrofluoric acid, we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of hydrofluoric acid = 2.35 kg

Theoretical yield of hydrofluoric acid = 3.20 kg

Putting values in above equation, we get:

$\%\text{ yield of hydrofluoric acid}=\frac{2.35g}{3.20g}\times 100\\\\\% \text{yield of hydrofluoric acid}=73.36\%$

Hence, the percentage yield of HF is 73.36 %

4 0

3 years ago

An atom with which atomic diagram is most similar to calcium?

Dominik [7]

Answer:

C

Explanation:

Calcium is an element with a total of 20 electrons.

It has 4 shells with a configuration of:

2, 8, 8, 2

Option C is the most similar to calcium but the number of shells is not complete.

It still requires two more shells with 8 and two electrons respectively.

3 0

2 years ago