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3 years ago

4. Consider the following reaction:

Chemistry

1 answer:

Lyrx [107]3 years ago

4 0

Answer:

High temperatures

Explanation:

NaHCO₃ (8) + HCH,O₂ (aq) → H₂O (l) + CO₂ (g) + NaC,H₃O₂ (aq)

As the flask gets cooler to the touch as the reaction proceeds, the reaction is endothermic. This means that ΔH is positive (ΔH>0).

As a gas is formed (bubbles are formed), ΔS is positive (ΔS>0).

<em>In terms of ΔG:</em>

ΔG = ΔH - TΔS

<em>In order for the reaction to be thermodynamically favorable, ΔH has to be negative</em>, thus:

The reaction is favorable if TΔS > ΔH.

The greater the temperature, the easier it would be for TΔS to be greater than ΔH.

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If the value for q is +450 J, what can you conclude about a process? A) it is endothermic and the temperature increased B) it is

yan [13]

Answer:

B) it is endothermic and the temperature decreased

Explanation:

Chemical reactions can be classified as endothermic and exothermic.

Endothermic reactions proceed with the absorption of heat energy (q) and have a positive value for q.

In contrast, Exothermic reactions proceed with the liberation of heat energy (q) and have a negative value for q.

It is given that the value of q = +450 J. Since q is positive, this implies that heat energy is absorbed from the surroundings resulting in a fall in temperature. Hence the reaction is endothermic.

7 0

3 years ago

Read 2 more answers

Question 1(Multiple Choice Worth 3 points)

Bingel [31]

1) Answer:

moles of oxygen (n) = 1.86 moles

Explanation:

according to Boyle's law the formula to solve this problem is:

PV=nRt

when P is the pressure which equal 1.25 atm

and V is the volume which equal 37.5 L

n is the number of moles which we need to calculate it

R is constant which equal 0.082

t is the temperature in kelvin

By substitution:

1.25*37.5 = n * 0.082 * 307

So n = 1.86 moles

2) Answer:

the volume of oxygen gas = 34 L

Explanation:

at standard temperature and pressure (STP) 1 mole of gas will equal = 22.4L

So when we have 1.5 moles of oxygen at standard temperature and pressure (STP) so we will estimate it like that

1.5 moles *22.4 L/ 1 mole = approximately 34 L

3) Answer:

The volume of H2 = 2.29 L

Explanation:

according to the Balanced equation we can see that the molar ratio between Zn and H2 1 : 1

so to know the number of moles of H2 we will get it for Zn first :

number of moles Zn = mass of Zn / molar mass Zn

= 5.98 / 65.39 =0.0914 moles

so number of moles H2 = 0.09 moles

by substitution in the following formula:

PV = nRT

0.978 * V = 0.09 * 0.082 * 298

so The volume of H2 = 2.29 L

4) Answer:

Volume of O2 = 1.4 L

Explanation:

first we have to balance the equation:

2Na2O2 +2CO2 → 2Na2CO3 + O2

2 mole CO2 give 1 mole of O2 so the molar ratio is 2:1

at STP 1 mole of gas will equal = 22.4 L

??? moles of CO2 = 2.8

n CO2 = 0.125 moles so n O2 = 0.125 /2 = 0.0625 moles

so when 1 mole of as = 22.4

0.0625 moles O2 = ???

Volume of O2 =0.0625 moles * 22.4 L/ 1 mole

= 1.4 L

5) Answer:

the initial quantity of sodium metal used = 17.2 gram

Explanation:

at STP 1 mole of gas will equal = 22.4 L

so moles of H2 equal ?? when 8.40 liters of H2 gas were produced

so moles of H2 = 8.4/22.4 =0.375 moles

and according to the balanced equation the molar ratio between H2 ans Na is 1 : 2

so number of moles for Na = 0.375 *2 = 0.75 moles

to get the initial quantity of sodium metal (mass Na) = number of moles * molar mass

mass Na = 0.75 moles * 23 gm/mole= 17.25

6) Answer:

False

Explanation:

because STP means standard temperature and pressure. and the Standard temperature must be 273 K and the standard pressure must be 1 atm but in the question the temperature is 298 K not 273 K so , It is not a standard temperature

7) Answer:

22.4 liters

Explanation:

1 mole of gas will equal = 22.4 L

because at the Standard temperature must be 273 K and the standard pressure must be 1 atm

so V = nRT/P

=1 mole * 0.082 * 273 K / 1 aTm

= 22.4 liters

4 0

4 years ago

Find the number of moles that are in 2.23 g of Li 2 O and report it with the correct significant figures.

Lesechka [4]

Not sure about the number of significant figures; you can decide where to round, but I would probably say 0.075mol.

8 0

3 years ago

The radius of a krypton atom is 110pm and it's mass is 1.39x10 to -22 g.

Readme [11.4K]

Answer:

$24.9~g/cm^3$

Explanation:

Density is found dividing mass by volume. In this case, we treat krypton as a sphere having a volume of $V = \dfrac{4}{3}\pi r^3$ . Given:

$m = 1.39\cdot 10^{-22}~g$

$r = 110 pm = 1.10\cdot 10^{-8}~cm$

We obtain density of:

$d = \dfrac{m}{V} = \dfrac{m}{\dfrac{4}{3}\pi r^3} = \dfrac{3m}{4\pi r^3}$

$d = \dfrac{3\cdot 1.39\cdot 10^{-22}~g}{4\pi\cdot (1.10\cdot 10^{-8}~cm)^3} = 24.9~g/cm^3$

This is not a feasible value for a gas like krypton, its radius is actually not 110 pm.

6 0

3 years ago

Which of the following represents the mass of 1 molecule of SH2?

mr_godi [17]

Answer:
5.645 × 10⁻²³ g

Solution:

Step 1) Calculate Molar Mass of SH₂;

Atomic Mass of Sulfur = 32 g/mol

Atomic Mass of H₂ = 2 g/mol
--------------------
Molecular Mass of SH₂ = 34 g/mol

Step 2: Calculate mass of one molecule of SH₂ as;

As,

Moles = # of Molecules / 6.022 × 10²³

Also, Moles = Mass / M.Mass So,

Mass/M.mass = # of Molecules / 6.022 × 10²³

Solving for Mass,

Mass = # of Molecules × M.mass / 6.022 × 10²³

Putting values,

Mass = (1 Molecule × 34 g.mol⁻¹) ÷ 6.022 × 10²³

Mass = 5.645 × 10⁻²³ g

5 0

4 years ago

Read 2 more answers