# SCIENCE/CHEM

posted by .

the purity of zinc is to be determined by measuring the amount of hydrogen formed when a weighed sample of zinc reacts with an excess of HCL acid.the sample weighs 0.198 grams. what amount of hydrogen gas at STP will be obtained if the zinc is 100% pure?
need a metric answer please thans andy

• SCIENCE/CHEM -

Stoichiometry problems are about the same.

1. Write the equation and balance it.
2. Convert 0.198 g Zn to moles. moles = grams/molar mass.
3. using the coefficients in the balanced equation, convert moles Zn to moles H2.
4. Convert moles H2 gas to volume. moles x 22.4 L/mol at stp or if grams, then g = moles x molar mass. The problem just says what amount, not how many grams or what volume.

• SCIENCE/CHEM -

Dr BOB,

Can you show me how to do the balanced equation please I am shocking at them
Thanks AndyWhats the simple way to explain balancing equations so i get it please....because i am horrible at them...
Thanks andy

• SCIENCE/CHEM -

Usually you have a word equation and you convert that to a symbol equation.
Zn + HCl ==> ZnCl2 + H2

Most of these can be balanced by trial and error. You learn to look for certain things. I would start this one by observing that I see 2Cl on the right and only 1 on the left. We can fix that with a coefficient of 2. (By the way, the first rule is that you may NOT balance the equation by changing subscripts. Once that equation is written as I have done above, the subscripts are set in stone.)
Back to the Cl. We can add a 2 to the HCl. (The ONLY way you CAN balance an equation is by changing coefficients. If one doesn't work we try another).
Zn + 2HCl ==> ZnCl2 + H2.
And it's balanced. I see 1 Zn on the left and right. 2H on left and right and 2 Cl on left and right. After you balance it you check it. You ALWAYS know if it is right or not. If it balanced it is right. If it doesn't balance it is wrong.).

• SCIENCE/CHEM -

thanks.... andy

## Similar Questions

1. ### Chem

A mixture of chromium and zinc weighing .362 g was reacted with an excess of hydrochloric acid. After all the metals in the mixture reacted 225 mL of dry hydrogen gas was collected at 27 C and 750 torr. Determine the mass percent Zn …
2. ### Chemistry

A mixture of chromium and zinc weighing .362 g was reacted with an excess of hydrochloric acid. After all the metals in the mixture reacted 225 mL of dry hydrogen gas was collected at 27 C and 750 torr. Determine the mass percent Zn …
3. ### chemistry

Zinc metal reacts with hydrochloric acid to produce hydrogen gas according to the equation below. What volume of hydrogen at STP is released when 15.1 grams of zinc react at STP?
4. ### chemistry

Zinc combines with hydrochloric acid to form aqueous zinc chloride and hydrogen gas.  If 300.0 mL of a 0.150  M solution of HCl is allowed to react with excess zinc, how many moles of hydrogen gas would be produced?
5. ### Chemistry

When 0.40 g of impure zinc reacted with an excess of hydrochloric acid, 127 mL of hydrogen was collected over water at 10 degress C The external pressure was 737.7 Torr. a) What volume would the dry hydrogen occupy at 1.00 atm and …
6. ### science

Al(s) + HCl(aq) AlCl3(aq) + H2(g) Zn(s) + HCl(aq) ZnCl2(aq) + H2(g) Consider the unbalanced equations above. A 0.250 g sample of a mixture of aluminum and zinc metal is reacted with an excess of hydrochloric acid. Both metals react …
7. ### Chemistry

Al(s) + HCl(aq) AlCl3(aq) + H2(g) Zn(s) + HCl(aq) ZnCl2(aq) + H2(g) Consider the unbalanced equations above. A 0.200 g sample of a mixture of aluminum and zinc metal is reacted with an excess of hydrochloric acid. Both metals react …
8. ### Science

zinc is mixed with Hydrochloric acid to form zinc chloride and hydrogen gas. if 7.3 grams of zinc completely reacts how much hydrogen gas will be created?
9. ### chemistry

A 0.052g sample of aluminium reacts with excess 6M HCL. A 48.3mL volume of hydrogen gas was collected over water at 22C and the pressure of the hydrogen gas was 751mmHg.calculate the aluminum percent purity in the sample. What volume …
10. ### chemistry

A common way of producing hydrogen gas in the lab is by reacting zinc with hydrochloric acid. Zn (s) + 2 HCl (aq) -> ZnCl2 (aq) + H2 (g) A sample of impure zinc, of mass 5.10g, reacted with an excess of hydrochloric acid solution …

More Similar Questions