5. If 10.0 gram of aluminum chloride are decomposed, how many molecules of Cl, are produced?

I have a 270 g cup of coffee at 94.1 degrees Celsius. Assume that the specific heat of coffee is the same as pure water, 4.18 J/

natulia [17]

Answer:

90.64 degrees

Explanation:

Lets list out the parameters given in the question.

Mass of Cup = 270g

Temp. of cup = 94.1C

Specific heat capacity of C = 4.18J/gC

Temp. of Silver spoon = 26.8C

heat capacity of the silver spoon = 61.2 J/C

The fact that thermal equilibrium was mentioned simply means that;

Heat Lost by coffee= Heat gained by spoon

The relationship between the parameters mentioned is given as;

Q = m* c * dT

Where;

m is the mass, c is the specific heat capacity and dT is the "change" in temperature.

Assume the final temperature of the whole system is "x". They would both have the same final temperature since they are in thermal equilibrium.

Heat lost by coffee = 270 * 4.18 * (94.1 - x)

(94.1 -x) because coffee will loose heat, hence temperature of coffee will fall.

Heat gained by spoon = c *dT = 61.2 * (x - 26.8).

dT = Final Temp. - Initial Temp.

dT = x - 26.8

Heat lost = Heat gained :

270 * 4.18 * (94.1 - x) = 61.2 * (x - 26.8),

1128.6 (94.1 - x) = 61.2 (x- 26.8)

18.44 ( 94.1 - x) = x - 26.8

1735.2 - 18.44 x = x - 26.8

1735.2 + 26.8 = x + 18.44 x

1762 = 19.44 x

x = 90.64 degrees

8 0

3 years ago

10) How many grams are there in 1.00 x 10^24 molecules of BC13?

lana66690 [7]

194.5 g of BCl₃ is present in 1 × 10²⁴ molecules of BCl₃.

Explanation:

In order to convert the given number of molecules of BCl₃ to grams, first we have to convert the molecules to moles.

It is known that 1 moles of any element has 6.022×10²³ molecules.

Then 1 molecule will have $\frac{1}{6.022*10^{23} }$ moles.

So $1*10^{24} molecules = \frac{1*10^{24} }{6.022*10^{23} } =1.66 moles$

Thus, 1.66 moles are included in BCl₃.

Then in order to convert it from moles to grams, we have to multiply it with the molecular mass of the compound.

As it is known as 1 mole contains molecular mass of the compound.

As the molecular mass of BCl₃ will be

$Molecular mass of BCl_{3}= Mass of Boron + (3*Mass of chlorine)$

Mass of boron is 10.811 g and the mass of chlorine is 35.453 g.

Molar mass of BCl₃ = 10.811+(3×35.453)=117.17 g.

$grams of BCl_{3}=Molar mass of BCl_{3}*Number of moles$

$grams of BCl_{3}=117.17*1.66=194.5 g$

So, 194.5 g of BCl₃ is present in 1 × 10²⁴ molecules of BCl₃.

3 0

4 years ago

Positive or negative , guys?

dalvyx [7]

I think it’s positive

5 0

3 years ago

What happens when sodium reacts with fluorine to produce sodium fluoride???

zalisa [80]

Balanced chemical reaction: 2Na(s) + F₂(g) → 2NaF(s) + energy.

This is exothermic reaction (energy or heat is released), because reactants have higher energy than products of reaction.

In ionic salt sodium fluoride (NaF), fluorine has electronegativity approximately χ = 4 and sodium χ = 1 (Δχ = 4 - 1; Δχ = 3), fluorine attracts electron and it has negative charge and sodium has positive charge.

3 0

3 years ago

Calcium carbide (CaC2) reacts with water to form acetylene (C2H2) and Ca(OH)2.

Sloan [31]

The answer is -60.57. With appropriate sig figs it becomes -60.6 KJ.

I think you were on the right track. However you need to multiply H2O by its coefficient from the balanced equation. Then you also need to keep in mind the signs. 

Maybe it's easier if I write what I did out: 

2H2O > 2H2 +O2...............-H= 2* -285.83 
Ca + O2 + H2 > Ca(OH)2....H= -986.2 
2C + H2 > C2H2.................H= 226.77 

The above H's stand for standard enthalpy of formations. These can be found in textbook appendix. Notice the negative infront of the enthalpy (H) for H2O. This is to remind me/you that the heat lost is gained in the rxn. 

So then you add them up. 226.77 - 986.2 + (2*285.83) = -187.77 

Add back the total enthalpy that is given in the question -187.77+127.2 = -60.57 

If signs cross you up find a way to remember that works for you.

4 0

4 years ago