4. Write a chemical formula for a compound that has two atoms of oxygen (0) and

fgiga [73]

Answer:

hshdhdhdhdbdbdbdbdbdbdbddddhddhrhrhrhrhhrdhhdhhhhhbbbbbbbbbbbhhhhhhhhrbbrhrhrbbdbdbddvvdvdvdvdbdbdbdbdbdbfbfhfhdhdhdhdhfhfhdhdgdhdhdhdhdgdhfhdhdhd

4 0

2 years ago

The invention of the microscope made it possible for scientists to _________

Vlad1618 [11]

B. the whole point of the microscope was to see small cells and examine them

5 0

3 years ago

Scoring: Your score will be based on the number of correct matches minus the number of incorrect matches. There is no penalty fo

jarptica [38.1K]

Answer:

a. Too close to zero

b. ΔS > 0

c. Too close to zero

d. ΔS < 0

e. ΔS > 0

Explanation:

In order to answer this question we need to compare the change in number of mol in the gas state for the products vs the reactants.

An increase in number moles gas leads to a positive change in entropy. Conversely a decrease will mean ΔS is negative.

Now we can solve the parts in this question.

a. H₂ (g) + F₂ (g) ⇒ 2 HF (g)

We have no change in the number of moles gas products minus reactants. Therefore is too close to zero to decide since there is no change in mol gas.

b. 2 SO₃ ( g) ⇒ 2 SO₂ (g) + O₂ (g)

We have three moles of gas products starting with 2 mol gas SO₂, therefore ΔS is positive.

c. CH₄ (g) + 2 O₂ (g) ⇒ CO₂ (g) + 2 H₂O (g)

Again, we have the same number of moles gas in the products and the reactants (3), and it is too close to zero to decide

d. 2 H₂S (g) + 3 O₂(g) ⇒ 2 H2O (g) + 2 SO₂ (g)

Here the change in number of moles gas is negative ( -1 ), so will expect ΔS < 0

e. 2H₂O₂ (l) ⇒ 2H₂O(l) +- O2(g)

Here we have 1 mol gas and 2 mol liquid produced from 2 mol liquid reactants, thus the change in entropy is positive.

3 0

3 years ago

What is the half-life of a 12 g sample of radioisotope that decayed to 6 g in 28

Charra [1.4K]

Answer:

A. 28 years

Explanation:

Applying,

R = R'(2ᵃ/ⁿ).............. Equation 1

Where R = Original sample, R' = Sample left after decay, a = Total time taken to decay, n = half life.

From the question,

Given: R = 12 g, R' = 6 g, a = 28 years.

Substitute into equation 1 and solve for n

12 = 6(2²⁸/ⁿ)

12/6 = 2²⁸/ⁿ

2²⁸/ⁿ = 2

Equation the base,

28/n = 1

n = 28 years.

Hence the half-life is 28 years

4 0

3 years ago

Suppose a salt and a glucose solution are separated by a membrane that is permeable to water but not to the solutes. the nacl so

stira [4]

1)

m(NaCl) = 1.95 g
V(H2O) = 250mL
M(NaCl) = 58.5 g/mole

Since waters density value is 1g/mL, it can be assumed that volume and mass of water are same values:

V(H2O) = 250ml = 250g = 0.25 kg

molality of NaCl:

n(NaCl)=m/M=1.95/58.5= 0.033 mole

molality b(NaCl)=n(NaCl) / V (H2O)= 0.033/0.25 = 0.132 mol/kg

milimolality of NaOH = 0.132/0,001 = 132 mmole/kg

milliosmolality of NaOH = milimolality x N of ions formed in dissociation

Since NaCl dissociates into 2 ions in solution:

milliosmolality of NaOH = 132 x 2 = 264 osmoles/kg

2)

m(gl) = 9 g
V(H2O) = 250mL
M(NaCl) = 180 g/mole

Since waters density value is 1g/mL, it can be assumed that volume and mass of water are same values:

V(H2O) = 250ml = 250g = 0.25 kg

molality of glucose:

n(gl)=m/M=9/180= 0.05 mole

molality b(gl)=n(gl) / V (H2O)= 0.05/0.25 = 0.2 mol/kg

milimolality of glucose = 0.132/0,001 = 200 mmole/kg

milliosmolality of glucose = milimolality x N of ions formed in dissociation

Since glucose does not dissociate, milimolality and milliosmolality are same:

milliosmolality of glucose = 200 osmoles/kg

3)

The osmosis represents the diffusion of solvent molecules through a semi-permeable membrane that allows passage solvent molecules but does not to the dissolved substance molecule. The osmosis occurs when the concentrations of the solution on both sides of the membrane are different. Since the semi-permeable membrane only permeates the solvent molecules, but not the particles of the dissolved substance, it occurs the solvent diffusion through the membrane, i.e. the solvent molecules pass through the membrane to equalize the concentration on both sides of the membrane. Solvents molecules move from the middle with a lower concentration in the middle with a higher concentration of dissolved substances.

In our case, osmosis will occur because the concentration of NaCl solution and the concentration of glucose solution do not have same values. Osmosis will occur in the direction of glucose solution because it has a lower concentration.

3 0

3 years ago