CHEMISTRY HIGH SCHOOL

How many moles of CaO form when 98.60 g CaCO3 decompose

Answers

Answer 1
Answer: The balanced reaction is:

CaCO3 = CaO + CO2

We are given the amount of CaCO3 to decompose when heated. This will be our starting point.

 

98.60 g CaCO3 ( 1 mol CaCO3 / 100.09 grams CaCO3) (1 mol CaO / 1 mol CaCO3 ) ( 56.08 g O2 / 1 mol CaO) =  55.25 g CaO
Answer 2
Answer:

0.9851mol.                      This is the rt answer just did it

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How many grams of oxygen are required to react with 10.0 grams of octane

Answers

are their any choice ?

A student observed that the rate of a chemical reaction increased as the temperature of the system increased. Which of the following statements best explains why thermal energy caused an increase in the reaction rate?A. The surface area of the product particles decreased.
B. The collision rate of the reactant particles increased.
C. The concentrations of the reactant particles increased.
D. The concentrations of the product particles decreased.

Answers

B, The increased thermal energy makes the particles move faster, making more collisions possible.
The answer is "B. The colllision rate of the reactant particles increased." because as you increase the temperature, the particles move faster and the faster the the particles move, the faster their collision rate.!!!

Why can't there be a temperature lower than absolute zero?

Answers

At absolute zero, there would be no energy left, and negative energy is unknown to us, so you cannot go lower than a state with no energy. Atoms would stop moving.

Match each of the following fat-soluble vitamins with the unit used to express the amount required in the diet. A: microgram. B: miligram

Answers

Since 1 milligram = 1000 microgram

Vitamin A, 1500 Microgram >>  1.5 Milligram

Vitamin C, 60,000 microgram >> 60 milligram

Vitamin D, 10 Microgram >> 0.01 Milligram

Vitamin K , 80 Microgram >> 0.08 Milligram

Vitamin E, 1,000,000 microgram >> 1000 milligram

It is possible for a particular element to have various number of neutrons

Answers

Yes, it is possible for a particular element to have various number of neutrons, and that would make it have an isotope. 

Pb(NO3)2 (aq) + 2 NaI (aq) --> PbI2 (s) + 2 NaNO3 (aq)Starting with with 50.0 grams of Pb(NO3)2 and 30.0 grams of NaI:
A. What is the limiting reagent?
B. How many grams of the excess reactant remains?
C. How many grams of each product is formed?
D. If 12 grams of NaNO3 actually formed in the reaction, what is the percent yield of this reaction?

Answers

Answer:

Explanation:

Pb(NO3)2 (aq) + 2 NaI (aq) --> PbI2 (s) + 2 NaNO3 (aq)

MM for each compound -

Pb(NO3): 207 + 14x2 + 16x3x2 = 331

PI2: 207 + 127x2 = 461

NaI: 23 + 127 = 150

NaNO3: 23 + 14 + 16x3 = 85

Moles of Pb(NO3)2 = 50/331 = 0.15

Moles of NaI = 30/150 = 0.2

Ratio of moles is 1:2

So NaI is limiting

Limited to 0.2/2 = 0.1 mole of Pb(NO3)2

Excess = 0.15 - 0.1 = 0.05 mole

Mass remains = 0.05x331 = 16.55 grams

Moles of NaNO3 formed = Moles of NaI reacted = 0.2

Mass = 0.2x85 = 17 grams

Moles of PbI2 formed = Moles of Pb(NO3)2 reacted = 0.1

Mass = 0.1x461 = 46.1 grams

If 12 grams of NaNO3 actually formed in the reaction,

percent yield = 12/17x100% = 70.6%

Answer:

Explanation:

Moles of Pb(NO3)2 =  mass/molecular mass

= 50.0 grams/(207.20*1 + 14.01*2 + 16*6)

= 50.0 grams/331.22

= 0.15 moles

Moles of NaI

= 30/(22.99+126.9)

= 30/149.89

= 0.2 Moles

A. NaI is less 2x Pb(NO3)2 so NaI is the limiting reagent.

B. The ratio is 1 to 2 so there is 0.15 - 0.2/2 = 0.05 mole

or 16.78 grams of Pb(NO3)2 left.

C. As NaI is limiting, only 0.2 Moles of NaNO3 is formed.

Mass =  Moles * Molecular Mass

Molecular Mass of NaNO3 can be calculated as:  

Na - 22.99

N - 14.01

O - 3(16) = 48

23+14+48 = 85gram / mole

Thus, Mass =  0.2*85  = 17 gram of NaNO3

Mass is conserved in a chemical reaction.

Mass of PbI2 can be calculated as:

50+30-16.78-17

= 46.3 gram of PbI2

Mass =  

12.75

Thus, 12.75g of Sodium Nitrate can be formed
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