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2 years ago

(08.04 MC)

Chemistry

1 answer:

Veronika [31]2 years ago

5 0

Answer:

Both have a pH greater than 7, but NH₃ has a lower pH than KOH.

Explanation:

Both of NH₃ and KOH are bases (can produce OH⁻), so both have a pH greater than 7.

NH₃ is considered as a weak base (not completely ionized), while KOH is a strong base (completely ionized).

If both NH₃ an KOH has the same concentration, KOH produces OH⁻ higher than that of NH₃.

So, NH₃ has a lower pH than KOH.

Thus the right choice is:

Both have a pH greater than 7, but NH₃ has a lower pH than KOH.

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An analytical chemist weighs out 0.188 g of an unknown triprotic acid into a 250 mL volumetric flask and dilutes to the mark wit

Anon25 [30]

Answer: The molar mass of unknown triprotic acid is 97.66 g/mol

Explanation:

To calculate the molarity of acid, we use the equation given by neutralization reaction:

$n_1M_1V_1=n_2M_2V_2$

where,

$n_1,M_1\text{ and }V_1$ are the n-factor, molarity and volume of triprotic acid

$n_2,M_2\text{ and }V_2$ are the n-factor, molarity and volume of base which is NaOH.

We are given:

$n_1=3\\M_1=?M\\V_1=250mL\\n_2=1\\M_2=0.0600M\\V_2=95.9mL$

Putting values in above equation, we get:

$3\times M_1\times 250=1\times 0.0600\times 95.9\\\\M_1=0.0077M$

To calculate the molecular mass of solute, we use the equation used to calculate the molarity of solution:

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

We are given:

Molarity of solution = 0.0077 M

Given mass of triprotic acid = 0.188 g

Volume of solution = 250 mL

Putting values in above equation, we get:

$0.0077M=\frac{0.188\times 1000}{\text{Molar mass of triprotic acid}\times 250}\\\\\text{Molar mass of triprotic acid}=97.66g/mol$

Hence, the molar mass of unknown triprotic acid is 97.66 g/mol

7 0

2 years ago

What is the application of flotation

Mumz [18]

Answer:

The law of floatation is applied in all vessels which travel by waterways that include ships, submarines and ferry boats. It is also applied in some vessels which travel by air ways such as hot air balloon and air ship. Balloons of different colors and shapes are filled with lighter gas so that will float in air.

4 0

2 years ago

Read 2 more answers

At what temperature is the following reaction feasible: HCl(g) + NH3(g) -> NH4Cl(s)?

Nutka1998 [239]

Energy is distributed not just in translational KE, but also in rotation, vibration and also distributed in electronic energy levels (if input great enough, bond breaks).

All four forms of energy are quantised and the quanta ‘gap’ differences increases from trans. KE ==> electronic.

Entropy (S) and energy distribution: The energy is distributed amongst the energy levels in the particles to maximise their entropy.

Entropy is a measure of both the way the particles are arranged AND the ways the quanta of energy can be arranged.

We can apply ΔSθsys/surr/tot ideas to chemical changes to test feasibility of a reaction:

ΔSθtot = ΔSθsys + ΔSθsurr

ΔSθtot must be >=0 for a chemical change to be feasible.

For example: CaCO3(s) ==> CaO(s) + CO2(g)

ΔSθsys = ΣSθproducts – ΣSθreactants

ΔSθsys = SθCaO(s) + SθCO2(g) – SθCaCO3(s)

ΔSθsurr is –ΔHθ/T(K) and ΔH is very endothermic (very +ve),

Now ΔSθsys is approximately constant with temperature and at room temperature the ΔSθsurr term is too negative for ΔSθtot to be plus overall.

But, as the temperature is raised, the ΔSθsurr term becomes less negative and eventually at about 800oCΔSθtot becomes plus overall (and ΔGθ becomes negative), so the decomposition is now chemically, and 'commercially' feasible in a lime kiln.

CaCO3(s) ==> CaO(s) + CO2(g) ΔHθ = +179 kJ mol–1 (very endothermic)

This important industrial reaction for converting limestone (calcium carbonate) to lime (calcium oxide) has to be performed at high temperatures in a specially designed limekiln – which these days, basically consists of a huge rotating angled ceramic lined steel tube in which a mixture of limestone plus coal/coke/oil/gas? is fed in at one end and lime collected at the lower end. The mixture is ignited and excess air blasted through to burn the coal/coke and maintain a high operating temperature.
ΔSθsys = ΣSθproducts – ΣSθreactants
ΔSθsys = SθCaO(s) + SθCO2(g) – SθCaCO3(s) = (40.0) + (214.0) – (92.9) = +161.0 J mol–1 K–1
ΔSθsurr is –ΔHθ/T = –(179000/T)
ΔSθtot = ΔSθsys + ΔSθsurr
ΔSθtot = (+161) + (–179000/T) = 161 – 179000/T
If we then substitute various values of T (in Kelvin) you can calculate when the reaction becomes feasible.
For T = 298K (room temperature)

ΔSθtot = 161 – 179000/298 = –439.7 J mol–1 K–1, no good, negative entropy change

For T = 500K (fairly high temperature for an industrial process)

ΔSθtot = 161 – 179000/500 = –197.0, still no good

For T = 1200K (limekiln temperature)

ΔSθtot = 161 – 179000/1200 = +11.8 J mol–1 K–1, definitely feasible, overall positive entropy change

Now assuming ΔSθsys is approximately constant with temperature change and at room temperature the ΔSθsurr term is too negative for ΔSθtot to be plus overall. But, as the temperature is raised, the ΔSθsurr term becomes less negative and eventually at about 800–900oC ΔSθtot becomes plus overall, so the decomposition is now chemically, and 'commercially' feasible in a lime kiln.
You can approach the problem in another more efficient way by solving the total entropy expression for T at the point when the total entropy change is zero. At this point calcium carbonate, calcium oxide and carbon dioxide are at equilibrium.
ΔSθtot–equilib = 0 = 161 – 179000/T, 179000/T = 161, T = 179000/161 = 1112 K

This means that 1112 K is the minimum temperature to get an economic yield. Well at first sight anyway. In fact because the carbon dioxide is swept away in the flue gases so an equilibrium is never truly attained so limestone continues to decompose even at lower temperatures.

8 0

2 years ago

Read 2 more answers

A car traveling at a constant speed travels 175 miles in four hours. How many minutes will it take for the car to travel 1000 fe

elena-14-01-66 [18.8K]

It takes 0.26 minutes to travel 1000 feet

Solution:

Given that car traveling at a constant speed travels 175 miles in four hours

Distance = 175 miles

Time taken = 4 hours

Convert the units to feet and minute

Given that,

1 mile = 5280 feet

175 miles = 5280 x 175 feet = 918720 feet

Also we know that,

1 hour = 60 minutes

4 hours = 60 x 4 minutes = 240 minutes

Thus, we got,

Distance = 918720 feet

Time taken = 240 minutes

Find the speed of car

Speed is given by formula:

$speed = \frac{distance}{time}$

$speed = \frac{918720}{240} = 3828$

Thus speed of car is 3828 feet per minute

How many minutes will it take for the car to travel 1000 feet?

Let "x" be the minutes needed for 1000 feet

speed of car is 3828 feet per minute

1 minute = 3828 feet

x minute = 1000 feet

This forms a proportion. We can solve by cross multiplying

$x \times 3828 = 1000 \times 1\\\\x = \frac{1000}{3828}\\\\x = 0.26$

Thus it takes 0.26 minutes to travel 1000 feet

7 0

3 years ago

A solution has a pH of 12. This solution is:

kolezko [41]

Answer:

basic

Explanation:

pH 7: neutral

12>7

so it is basic

(if <7 than acidic)

3 0

2 years ago