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3 years ago

Why is it important to determine the qcalorimeter before determining the qmetal?

2 answers:

8 0

In order to determine the heat absorbed or given by a metal it is important to determine the heat loss or gained by calorimeter

If we dip a hot metal piece in a calorimeter, it will lose energy which will be absorbed by calorimeter

The heat absorbed by calorimeter = heat loss by metal

the heat absorbed by calorimeter = heat capacity of calorimter X change in temperature

so we should have the value of heat absorbed by calorimeter which will be equal to the heat loss by metal

heat loss by metal = mass of metal X specific heat of metal X change in temperature

thus we can calculate the specific heat of metal.

nataly862011 [7]3 years ago

7 0

To find the enthalpy change per mole of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final temperatures (before the reaction started and after it has finished) are noted

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Please help!!!!its due tomorrow !!!

scZoUnD [109]

#6).
Every 1,000 mL makes 1 L
How many 1,000mL are there in 2,800 mL ?
That's division.
 (2,800 mL) / (1,000 mL) = 2.8 L

#7).
The 'perimeter' means the 'distance all the way around'.
You have to know that both sides of a rectangle are the same length,
and also the top and bottom are the same length.
So the perimeter of this rectangle is

 (2 yd) + (4.5 yd) + (2.yd) + (4.5 yd) = 13 yd .

Oops. The problem wants to know the perimeter in feet.
So you have to know that each yard is the same as 3 feet.
In order to find the number of feet in 13 yards, you have to
take 3 feet 13 times .

 (3 feet) times (13) = 39 feet .

#8).
For this one, you have to know that every 36 inches makes 1 yard.

How many 36 inches are there in 48 inches ?
That's division.
 (48 inches) / (36inches) = 1 and 1/2 yards .

#9).
For this problem, you have to know how to handle a mixed number,
and you also have to know that there are 16 ounces in 1 pound.

Add up the fruit:

 (3-1/2 pounds) + (4 pounds) + 2 pounds) = 9-1/2 pounds

Now, remember that each pound is the same as 16 ounces. So if you
want to find the number of ounces in 9-1/2 pounds, you have to take
16 ounces 9-1/2 times .

 (16 ounces) times (9-1/2) = 152 ounces.
___________________________________

#10).
This one is just adding up some numbers. But after you finish doing that, you have to know that 1,000 meters is called '1 kilometer' .

Add up the distances that Omar ran:

 (1,000 meters) + (1,625 meters) + (1,500 meters) = 4,125 meters

The problem wants to know how many kilometers this is, so you have to figure out how many '1,000 meters' fit into 4,125 meters.

That's division.

 (4,125 meters) / (1,000 meters) = 4.125 kilometers

4 0

4 years ago

Consider the titration of 1L of 0.36 M NH3 (Kb=1.8x10−5) with 0.74 M HCl. What is the pH at the equivalence point of the titrati

worty [1.4K]

Answer:

Explanation:

The question asks to calculate the pH at equivalence point of the titration between ammonia and hydrochloric acid

Firstly, we write the equation of reaction between ammonia and hydrochloric acid.

NH3(aq)+HCl(aq)→NH4Cl(aq)

Ionically:

HCl + NH3 ---> NH4 + Cl-

Firstly, we calculate the number of moles of the ammonia as follows:

from c = n/v and thus, n = cv = 0.36 × 1 = 0.36 moles

At the equivalence point, there is equal number of moles of ammonia and HCl.

Hence, volume of HCl = number of moles/molarity of HCl = 0.36/0.74 = 0.486L

Hence, the total volume of solution will be 1 + 0.486 = 1.486L

Now, we calculate the concentration of the ammonium ions = 0.36/1.486 = 0.242M

An ICE TABLE IS USED TO FIND THE CONCENTRATION OF THE HYDROXONIUM ION(H3O+). ICE STANDS FOR INITIAL, CHANGE AND EQUILIBRIUM.

NH4+ H2O ⇄ NH3 H3O+

I 0.242 0 0

C -X +x +X

E 0.242-X X X

Since the question provides us with the base dissociation constant value K b, we can calculate the acid dissociation constant value Ka

To find this, we use the mathematical equation below

K a ⋅ K b = K w

, where K w- the self-ionization constant of water, equal to

10 ^-14 at room temperature

This means that you have

K a = K w.K b = 10 ^− 14 /1.8 * 10^-5 = 5.56 * 10^-10

Ka = [NH3][H3O+]/[NH4+]

= x * x/(0.242-x)

Since the value of Ka is small, we can say that 0.242-x ≈ 0.242

Hence, K a = x^2/0.242 = 5.56 * 10^-10

x^2 = 0.242 * 5.56 * 10^-10 = 1.35 * 10^-10

x = 0.00001161895

[H3O+] = 0.00001161895

pH = -log[H3O+]

pH = -log[0.00001161895 ] = 4.94

7 0

3 years ago

Which type of front occurs when cold air and warm air are next to each other, but are at a standstill?

noname [10]

Occluded font. For sure

8 0

3 years ago

the polio virus is 25 nanometers in diameter. How many would fit across the head of a pin 2 millimeters in diameter

IrinaVladis [17]

2mm=2,000,000 nm
2,000,000/25=80,000
The answer is 80,000 polio viruses

6 0

3 years ago

Read 2 more answers

A certain substance, X, has a triple-point temperature of 20°C at a pressure of 2.0 atm.

nikitadnepr [17]

Answer: The statement which could possibly not be true is C -" Liquid X can exist as a stable phase at 25°C, 1atm."

Explanation:

Triple point is the point where a substance co-exist as solid liquid and gas. At any point other than the triple point, the substance exist as a single phase substance.

As shown in the diagram, Liquid cannot exist as a stable phase at 1atm( below the the triple point pressure of 2atm) as the liquid can only exist beyond the pressure of triple point.

3 0

3 years ago