Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: RydbergConstant on October 19, 2007, 02:36:32 AM
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I'm doing a practice test to review for a major test tomorrow and I need help on the following problems por favor! We're learning about concentration, dilution, molarity, thermochemistry, electromagnetic spectrum, quantum numbers, and anything else i've forgotten in that general range.
A 5.00 sample of sodium chloride was dissolved in water to form 250. mL of solution. What is the molar concentration of the solution?
Answer: 0.342 M
Which of the following photons carries the SMALLEST amount of energy?
a)a photon with the wavelegnth of 656 nm
b) a photon with the frequency of 1.4E14 s^-1
c) a photon of UV light
d) a photon of yellow light
e) a photon with the energy of 2.04E-18 J
Answer: B
Thanks!!
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Assuming you meant 5.00 g answer to 1st question is OK.
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Yea I was trying to figure out if my professor had mistyped it because it made no sense at all. At first I thought it was 5.00 mol, but I worked it out with grams like you said and it makes sense! So you know how to work out the second problem??
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So you know how to work out the second problem??
Use the fact that E = hf = hc/lambda.
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Ahh!! Actually what about this problem:
Acids and bases undergo a neutralization reaction in which a salt and water are formed. What is the molar concentration(molarity) of the hydrochloric acid solution, if 36.0 mL of it requires 18.9 mL of 0.213 M of the calcium hydroxide solution to get neutralized:
Ca(OH)2(aq) + 2HCl(aq) --> CaCl2(aq) + 2H2O(l)
Answer: 0.224 M
What equation do I use for this??
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So you know how to work out the second problem??
Use the fact that E = hf = hc/lambda.
Thank you!
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Acids and bases undergo a neutralization reaction in which a salt and water are formed. What is the molar concentration(molarity) of the hydrochloric acid solution, if 36.0 mL of it requires 18.9 mL of 0.213 M of the calcium hydroxide solution to get neutralized:
Ca(OH)2(aq) + 2HCl(aq) --> CaCl2(aq) + 2H2O(l)
Answer: 0.224 M
What equation do I use for this??
n=cv
Find moles of Calcium hydroxide. How many moles of HCl are needed to neutralise this?
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Acids and bases undergo a neutralization reaction in which a salt and water are formed. What is the molar concentration(molarity) of the hydrochloric acid solution, if 36.0 mL of it requires 18.9 mL of 0.213 M of the calcium hydroxide solution to get neutralized:
Ca(OH)2(aq) + 2HCl(aq) --> CaCl2(aq) + 2H2O(l)
Answer: 0.224 M
What equation do I use for this??
n=cv
Find moles of Calcium hydroxide. How many moles of HCl are needed to neutralise this?
It doesn't say how many moles of HCl are needed to neutralize it
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Acids and bases undergo a neutralization reaction in which a salt and water are formed. What is the molar concentration(molarity) of the hydrochloric acid solution, if 36.0 mL of it requires 18.9 mL of 0.213 M of the calcium hydroxide solution to get neutralized:
Ca(OH)2(aq) + 2HCl(aq) --> CaCl2(aq) + 2H2O(l)
Answer: 0.224 M
What equation do I use for this??
n=cv
Find moles of Calcium hydroxide. How many moles of HCl are needed to neutralise this?
It doesn't say how many moles of HCl are needed to neutralize it
It does. Your rxn eqn gives you this info. It will be twice number of mole of Ca(OH)2.
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I get it now! Thanks!! You were a major help