Can someone please check-over my answers to these Chemistry problems?

Question

1. What is the molality of a solution in which 1.50 × 10² g of Magnesium Nitrate, Mg(NO₃)₂, are dissolved in 400.0 g of warm water?

A. 0.5 m

B. 0.5 M

C. 2.53 m

D. 2.53 M

E. None of the Above

 

2. How many grams of CaCl₂ are needed to make a solution with a concentration of 3.0 m from 2.25 kg of water?

A. 74.9 g CaCl2

B. 749.9 kg CaCl2

C. 7.50 kg CaCl2

D. 7.5 x 102 g CaCl2

E. 7.5 × 10–2 g CaCl2

 

3. What is the molality of a solution made from 1.56 moles of KCl and 1.22 kg of water at 200 ^oF?

A. 1.28 m

B. 1.28 M

C. 12.84 m

D. 12.84 M

E. All of the Above

 

4. For the reaction KOH (aq) + HCN (aq) → H₂O (l) + KCN (aq), what volume of HCN at 2.00 M would be required in order to make 33.0 g of KCN, when there is more HCN than needed?

A. 25.3 L

B. 2.53 L

C. 0.253 L

D. 0.0253 L

E. 2.53 mL

Answer 1

Hello, Jesset,

Thanks for providing your proposed answers. Here are my comments:

1. My original reponse incorrectly used 0.8 kg solvent. The correct vale of 0.4kg gives the 2.53 answer you have selected. Thaks to J.R. S. for pointing that out.
2. I also calculate 750g CaCl₂
3. Agree: 1.28m
4. Very good - Agree with 253 ml

Bob