Chemistry Question Homework...Solutions to problems would be great!?

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notachemist

New member
I'm in desperate need of help. Could anyone help with the answers and how to work out the problems. Thanks

Question 1
How many moles of C are in each of the following
75g of C
a) 0.25 moles of C2H6
b) 88g of CO2


Question 2
Balance the equation
a) Al(s) +H2SO4(aq)--->Al2(SO4)3(aq) + H2(g)
b) K2SO4(aq) + BaCl2(aq)----> BASO4(s) +KCl(aq)

Question 3
Calcium cyanamide reacts with water to form calcium Carbonate and ammonia
CaCN2(s) +3H2O(l)----> CaCO3(s) + 2NH3(g)

A) How many grams of water are needed to react with 75.0 g of CaCN2?
b) How many grams of NH3 are produced from 5.24 g of CaCN2
C) How many grams of CaCO3 form if 155 g of water reacts?

Question 4
Calculate the new temperature in degrees Celsius when pressure is changed with n and V constant.
a) a tank of helium gas with a pressure of 250 torr at O degrees Celsius is heated to give a pressure of 1500 torr
b)a sample of air at 40 degree celsius and 740 mmHg is cooled to give a pressure of 680 mmHg

Question 5
Aluminum oxide is formed from its elements
4Al(s) + 3O2(g)----> 2Al2O3(s)

How many grams of Al will react with 12.0 L of O2 at STP?
 
Considering that I like Chemistry I've decided to help you =D.

Problem 1 uses the percent composition formula, which we did at the beginning of last year and I forgot it, sorry =( try googling it! Use the formula for converting moles to grams and vice versa first then use the percent composition formula.

Problem 2 is simple.

For simplicity sake I'll use 1 if that part of the equation is already balanced.

2 Al + 3 H2SO4 --> 1 Al2(SO4)3 + 3 H2

1 K2SO4 + 1 BaCl2 --> 1 BaSO4 + 2 KCl

Problem 3 I'm really not sure how to do. Sorry.

Problem 4...

The formula used is PV = nRT
P is pressure, V is volume, n is moles, R is a constant, and T is temperature.

For simplicity sake, we will define torr as mmHg or millimeters of mercury.

Temperature in these equations uses K or Kelvins, 0 degrees Celsius is 273K.

initial values
=========
250 mmHg
273 K

final values
=========
1500 mmHg
x K

This can be solved using Charles Law, which is more simple.

mmHg is a unit of pressure.

P1 / T1 = P2 / T2

250 mmHg / 273 K = 1500 mmHG / x K

This comes out to 1638 K.

1638 K - 273 = 1365 degrees Celsius.

Part B.

initial
=====
40 celcius + 273 = 313 K
740 mmHg

final
====
x K
680 mmHg

same formula as last time.

740 mmHg / 313 K = 680 mmHg / xK

287.62 K

minus 273 to get back to celsius

14.62 degrees celsius

if your teacher cares about significant figures, the answer is just 10 degrees since 40 degrees only has 1 significant figure.

To be honest, I'm not too sure how to do question 5 and im feeling a little lazy been spending like 20 mins on these problems lol...

sorry for the bad grammar I got lazy after doing math

Good luck with the rest!
 
Considering that I like Chemistry I've decided to help you =D.

Problem 1 uses the percent composition formula, which we did at the beginning of last year and I forgot it, sorry =( try googling it! Use the formula for converting moles to grams and vice versa first then use the percent composition formula.

Problem 2 is simple.

For simplicity sake I'll use 1 if that part of the equation is already balanced.

2 Al + 3 H2SO4 --> 1 Al2(SO4)3 + 3 H2

1 K2SO4 + 1 BaCl2 --> 1 BaSO4 + 2 KCl

Problem 3 I'm really not sure how to do. Sorry.

Problem 4...

The formula used is PV = nRT
P is pressure, V is volume, n is moles, R is a constant, and T is temperature.

For simplicity sake, we will define torr as mmHg or millimeters of mercury.

Temperature in these equations uses K or Kelvins, 0 degrees Celsius is 273K.

initial values
=========
250 mmHg
273 K

final values
=========
1500 mmHg
x K

This can be solved using Charles Law, which is more simple.

mmHg is a unit of pressure.

P1 / T1 = P2 / T2

250 mmHg / 273 K = 1500 mmHG / x K

This comes out to 1638 K.

1638 K - 273 = 1365 degrees Celsius.

Part B.

initial
=====
40 celcius + 273 = 313 K
740 mmHg

final
====
x K
680 mmHg

same formula as last time.

740 mmHg / 313 K = 680 mmHg / xK

287.62 K

minus 273 to get back to celsius

14.62 degrees celsius

if your teacher cares about significant figures, the answer is just 10 degrees since 40 degrees only has 1 significant figure.

To be honest, I'm not too sure how to do question 5 and im feeling a little lazy been spending like 20 mins on these problems lol...

sorry for the bad grammar I got lazy after doing math

Good luck with the rest!
 
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