exponential decay

The​ half-life of a radioactive substance is 33.9 years.a. Find the exponential decay model for this substance.b. How much of the sample of 1000 grams will remain after 20 ​years?c. How long will... more

12/03/18

Chemistry - Mole to Mole Ratio

In a classic acid - metal reaction, hydrochloric acid reacts with aluminum to make aluminum chloride and hydrogen gas.2Al + 6HCl --> 2AlCl3 + 3H2If I start with 31.9 grams of zinc, how many... more

10/17/18

hard question, please help

Cobalt (II) chloride is commonly obtained from chemical supply houses as a hydrate with the formula CoCl2* 6 H2O. An analysis showed that 25.0 g of this hydrate contains 11.3 g of water. What is... more

Chemistry homework help

Write a balanced metathesis equation for the reaction which takes place when the two solutions described below are combined and then determine the amount of solid product produced. 250.0 ml of... more

Chemistry HW

The metathesis reaction between sodium carbonate and cobalt (III) chloride is shown below 3 Na2CO3 (aq) + 2 CoCl3 (aq) ➝ Co2(CO3)3 (s) + 6 NaCl (aq)How many grams of solid cobalt (III) carbonate... more

09/29/18

Chemistry Hw

 425.0 ml of 0.120 M Na2SO4 solution is added to 275.0 ml of 0.360 M NaNO3 solution. Calculate the final concentration of sodium ions in solution. You may assume that the volumes are additive. 

09/13/18

Heat Equation

A 40 gram piece of zinc at 45 celsius is placed in a beaker of cool water. If the zinc loses 375 joules of energy as it is cooled to 21 Celsius, determine the specific heat capacity of zinc.

09/13/18

Calculate the mass of sodium acetate (CH3COO0Na) required to make 500 ml of 0.375 molar aqeous solution . Molar mass of sodium acetate is 82.0245 g mol

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07/28/18

How do you solve this?

Write out the balanced equation for the reaction that occurs when Ca and Al(NO3)3 react together. You do not need to make your subscripts smaller; just write them out as regular numbers. For... more

07/28/18

How do you solve this chemistry problem?

Write out the balanced equation for the reaction that occurs when Ca(OH)2 and H3PO4 react together. You do not need to make your subscripts smaller; just write them out as regular numbers. For... more

I can't understand sum of numbers.

The sum of three numbers is 131. The third number is 4 times the first. The first number is 5 less than the second what are the numbers?

07/11/18

How many milligrams of aluminum nitrate contains 3.5 x 1018 oxygen atoms?

Mass of aluminum

07/04/18

What is the percent yield of H2 if 58.94g of methane yields 14.61g of H2

What is the percent yield of H2 if 58.94g of methane yields 14.61g of H2 for the following reaction: CH4(g) + 2H2O(g)->4 H 2 (g) + CO2(g)

Why is the pH of the first equivalence point, of a titration of polyprotic acid, not equal to7?

A titration of phosphoric acid with sodium hydroxide. The first equivalence point has a pH of about 5.    My thoughts are that because it is only the first equivalence point, only one H+ has been... more

06/15/18

word problem

A 300-gram salt and water solution contains 25 g of salt. This mixture is left in the open air and 100 g of water evaporates from the solution. What is the percent concentration of salt in the... more

06/11/18

Using standard heats of formation, calculate the standard enthalpy change for the following reaction.

Using standard heats of formation, calculate the standard enthalpy change for the following reaction. Fe(s) + 2HCl(aq)FeCl2(s) + H2(g)

06/09/18

How many grams of CH3NH3Cl were used up?

0.63 g of methyl amine was produced by the reaction: CH3NH3Cl +NaOH ---> CH3NH2 + NaCl +H2O . (1)How many grams of CH3NH3Cl were used up?

06/05/18

A solution is prepared by dissolving 100.00g sucrose (mm of sucrose = 343g) in 50g water. The volume of the resulting solution is 52mL. Calculate the ff.

A) Molarity B) Molality C) Mole fraction  D) mass % E) density of the solution

Ion Concentration/Dissociation

What is the concentration of each ion of the resulting solution when 18.5 mL of 0.25 M Al(NO3)3 is mixed with 22.4 mL of 0.50 M Cu(NO3)3?

the product of two consecutive intergers is 6 less than 3 times the sum

the product of two consecutive intergers is 6 less than 3 times the sum

A mixture of argon and xenon gases is maintained in a 8.89 L flask

A mixture of argon and xenon gases is maintained in a 8.89 L flask at a pressure of 2.36 atm and a temperature of 22 °C. If the gas mixture contains 16.2 grams of argon, the number of grams of... more

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