Chemistry - May 2007

Which of the following is not a heteroatom?

a. P
b. N
c. O
d. A and B
e. All of the above are heteroatoms.

2007-05-02 13:40:28 · 1 answers · asked by num1grl 2

iodide salt is formed. Calculate the empirical formula of this salt?

2007-05-02 13:40:04 · 2 answers · asked by Anonymous

Oxygen gas is added to a rebreather at the same rate as it would be in the open air. The volume is 4.8 dm3 and the temperature is 25 °C. The pressure is1 atm. Once the tank is lowered under the water the pressure increases to 2 atm and the temperature drops to 12 °C. Is the tank in danger of exploding if it's maximum volume is 5.0 dm3?

2007-05-02 13:38:03 · 1 answers · asked by Anonymous

2007-05-02 13:35:26 · 1 answers · asked by Anonymous

You have a sample of bone collected from Nevada and you find that it contains strontium-90 and exhibits an activity of 2.5 Bq. How much strontium-90 was present in the bone when the animal died 45 years ago. The half-life of 90Sr is 29 years.

a 1.1 x 10^8

b 9.7 x 10^8

c 3.3 x 10^8

d 1.5 x 10^8

2007-05-02 13:35:03 · 1 answers · asked by chemrob3 1

Judy is furious with her boyfriend, Richard for forgetting her birthday on August 25th. Richard swears that he bought a several balloons for her but they popped. He tries to explain scientifically by saying that the store clerk filled each 1.50 L balloon with Helium at the room temperature of the mall, a cool 23 oC. When he took the balloons in his car, he says the temperature was 30 oC and this caused the balloons to inflate past their maximum size of 1.55 L. Was Richard lying? (Hint: Calculate the final volume of the balloon and compare it to the maximum size!)

2007-05-02 13:34:31 · 2 answers · asked by Anonymous

25.00% nitrogen, and 28.55% oxygen and has a molar mass between 2010 and 2020?

2007-05-02 13:28:28 · 1 answers · asked by Anonymous

Calculate the equilibrium constant for the following reaction at 25°C, given that E°cell = +0.67 V

2Cr^2+(aq) + S4O6^2-(aq) → 2Cr^3+(aq) + 2S2O3^2-(aq)

a 2.08 × 10^11

b 1.86 × 10^45

c 4.32 × 10^22

d 6.53 × 10^9

2007-05-02 13:25:33 · 1 answers · asked by chemrob3 1

and the balance, phosphorus, what is the molecular formula?

2007-05-02 13:23:29 · 1 answers · asked by Anonymous

please let me know if you know the answer.

2007-05-02 13:22:51 · 2 answers · asked by craza_gurl014 1

A sample of 245Am has a t1/2 of 7.37 × 10^3 y and an activity value, A, of 1.00 Bq. How many nuclei are there initially and after 1,000 years.

a. Ni = 3.35 × 1011 nuclei;
N1000 = 2.32 × 1011 nuclei.

b Ni = 3.35 × 1011 nuclei;
N1000 = 3.05 × 1011 nuclei.

c Ni = 2.32 × 1011 nuclei;
N1000 = 3.32 × 1011 nuclei.

d Ni = 1.06 × 104 nuclei;
N1000 = 9.7 × 103 nuclei.

2007-05-02 13:22:14 · 1 answers · asked by chemrob3 1

Given the reaction A + B <--> AB + 210kJ, if an activation energy of 21kJ is required, the activation of the reverse reaction would be...?? would it also be 210kJ? or would it be 21??
also...
When a catalyst is added to a system at equilibrium, there is a decrease in the activation energy of...
a. only the forward reaction
b. only the reverse reaction
c. both forward and reverse reaction
d. neither forward nor reverse

thanks!

2007-05-02 13:11:40 · 1 answers · asked by Nicole S 1

The standard oxidation potential of the hydrogen electrode in a 1.00M solution of H3O+ is _____?

2007-05-02 13:07:37 · 1 answers · asked by Anonymous

1) Elements in the third row or lower can have how many octects?

2) internuclear distance is what bond?

2007-05-02 12:53:38 · 1 answers · asked by babes 1

when 0.500 grams of chromium metal is heated in excess iodine, 4.1505 grams of a chromium iodide salt is formed. Calculate the empirical formula for this salt.

2007-05-02 12:23:56 · 1 answers · asked by 41 1

Does anyone know the formula to find Parts Per Million (PPM) from the resistance (milivolts)?

2007-05-02 12:09:02 · 1 answers · asked by Jason C 1

2007-05-02 11:57:19 · 1 answers · asked by tommarowiii 1

1) Which of the following is amphoteric? diethyl ether, sodium phosphate, barium hydroxide, aluminum hydroxide, chloric acid

2) A reaction is observed to produce a colorless, odorless gas. Which of the following tests would indicate the precence of carbon dioxide? a glowing splint would make a 'pop' sound with the gas, bubbling the gas through water would make it basic, a glowing splint would reignite in the gas, the gas would react with dilute ammonia solution to create a precipitate, a glowing splint would extinguish in the gas

3) what would be the volume of gas produced at STP from the reaction of .3 mole magnesium and 2 moles hydrochloric acid?

2007-05-02 11:55:14 · 1 answers · asked by Anonymous

I know temperature 1 equals 423 K. For temperature 2, do i use 423K too or do I use 273?

2007-05-02 11:54:03 · 1 answers · asked by Yup 1

Metallic magnesium can be made by the electrolysis of molten MgCl2.
(a) What mass of Mg is formed by passing a current of 6.75 A through molten MgCl2 for 3.88 days? in grams

(b) How many minutes are needed to plate out 10.00 g Mg from molten MgCl2 using 2.50 A current?

2007-05-02 11:52:58 · 1 answers · asked by Anonymous

2007-05-02 11:51:06 · 1 answers · asked by zainab 1

1)when bubbled through calcium hydroxide solution, which will produce a white precipitate? hydrogen gas, carbon dioxide gas, ammonia gas, chlorine gas, oxygen gas.

2) which of the following substances would not form a colored solution in water? vanadium(III) chloride, zinc nitrate, iodine

3) which of the following would not have an exothermic heat of solution? potassium nitrate, nitric acid, calcium oxide

4) when added to chloroform, which would result in a purple solution? iodine, potassium permangonate, sodium chromate, mercury metal, lead(II) oxide

5) which is insoluble in both water and sulfuric acid? magnesium hydroxide, copper(II) sulfate, lead(II) nitrate, calcium chloride, mercury(II) sulfate

6) which has the highest melting point? silicon dioxide, oxygen, mercury, carbon tetrachloride, nickel(II) chloride

7) In a reaction with iron (II) sulfate, which would get oxidized? chlorine, choride, sulfur, aluminum, sulfide

Answer them if you can...

2007-05-02 11:50:43 · 2 answers · asked by Anonymous

2007-05-02 11:37:22 · 1 answers · asked by david j 1

2007-05-02 11:36:16 · 1 answers · asked by david j 1

by opening a stopcock connecting the two samples? Also, what will be the total pressure of the system?

(STP = Standard Temperature and Pressure; ST = 273 K and SP = 1 atm)

2007-05-02 11:34:14 · 1 answers · asked by Anonymous

i was given, magnesium hydroxide + phosphoric acid,
im supposed to tell what they yeild, what type they are such as aqueous, gasous etc., & what kind of reaction.

i know that magnesium hydroxide is a base and phosphoric acid is an acid, so they will yeild water and a salt. I know it is also a double displacement. But i cant balance it?


so this is what i came up with:

Mg(OH)2 + PO4 ------> H2O + Mg3 (PO4)2

but my problem is that i cant balance it? Im usually good at this but i cant figure out what im doing wrong? can someone help me?

2007-05-02 11:24:51 · 3 answers · asked by Breanna 2

At what temperature does delta H = T delta S for the phase change of liquid water to gaseous water at 1 atm?

2007-05-02 11:24:22 · 1 answers · asked by rnjes21 2

2007-05-02 11:20:14 · 1 answers · asked by Geddy_V 2

* Also called "hydroxyl acid", the substance is the major component of acid rain;
* Contributes to the greenhouse effect;
* Contributes to the erosion of our natural landscape;
* Accelerates corrosion and breakdown of electrical equipment;
* Excessive ingestion may cause various unpleasant effects;
* Prolonged contact with its solid form results in severe tissue damage;
* Inhalation, even in small quantities, may cause death;
* Its gaseous form may cause severe burns;
* It has been found in the tumors of terminal cancer patients;
* Withdrawal by those addicted to the substance causes certain death within 168 hours;

2007-05-02 11:18:39 · 2 answers · asked by Barkley Hound 7

between saturated and unsaturated fat?

2007-05-02 11:14:40 · 8 answers · asked by Turnip 3