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3 years ago

14

In order to increase the rate of a reaction, heat may not always be the best option. Describe why someone might choose to add a

catalyst instead of heat.

1 answer:

Kay [80]3 years ago

3 0

Catalysts provide alternate pathways which speed up the rate of the reaction and don't undergo any permanent chemical change.

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In a science experiment, Javi concludes that a chemical reaction has occurred. What evidence would support this conclusion?

Naily [24]

Answer:

B) a substance's color and odor changed Explanation: A signal that a chemical change has occurred is when its odor (its smell) or its appearance has changed.

8 0

2 years ago

Read 2 more answers

1. Land-dwelling creatures depend on the the water cycle to ___________ fresh water from its salt solution in the Earth's oceans

Novosadov [1.4K]

1 is evaporate and 2 is precipitate

3 0

2 years ago

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You need to prepare a solution with a specific concentration of Na+Na+ ions; however, someone used the end of the stock solution

babymother [125]

Explanation:

Ionic equation

NaCl(aq) --> Na+(aq) + Cl-(aq)

Na2SO4(aq) --> 2Na+(aq) + SO4^2-(aq)

In NaCl solution, 1 mole of Na+ is dissociated in 1 liter of solution while in Na2SO4, 2 moles of Na+ is dissociated in 1 liter of solution.

Molecular weight of NA2SO4 = (23*2) + 32 + (16*4)

= 142 g/mol

Molecular weight of NaCl = 23 + 35.5

= 58.5 g/mol

Masses

% Mass of NA+ in Na2SO4 = mass of Na+/total mass of Na2SO4 * 100

= 46/142 * 100

= 32.4%

% Mass of NA+ in NaCl = mass of Na+/total mass of NaCl * 100

= 23/58.5 * 100

= 39.3%

Therefore, the % mass of Na+ in NaCl and Na2SO4 are different so it cannot be used.

7 0

3 years ago

In this experiment we will be using a 0.05 M solution of HCl to determine the concentration of hydroxide (OH-) in a saturated so

gulaghasi [49]

<u>Answer:</u> The moles of hydroxide ions present in the sample is 0.0008 moles

<u>Explanation:</u>

To calculate the concentration of acid, we use the equation given by neutralization reaction:

$n_1M_1V_1=n_2M_2V_2$

where,

$n_1,M_1\text{ and }V_1$ are the n-factor, molarity and volume of acid which is HCl.

$n_2,M_2\text{ and }V_2$ are the n-factor, molarity and volume of base which is $Ca(OH)_2$

We are given:

$n_1=1\\M_1=0.05M\\V_1=16mL\\n_2=2\\M_2=?M\\V_2=36.0mL$

Putting values in above equation, we get:

$1\times 0.05\times 16=2\times M_2\times 36\\\\M_2=\frac{1\times 0.05\times 16}{2\times 36}=0.011M$

To calculate the moles of hydroxide ions, we use the equation used to calculate the molarity of solution:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}$

Molarity of solution = 0.011 M

Volume of solution = 36.0 mL

Putting values in above equation, we get:

$0.011=\frac{\text{Moles of }Ca(OH)_2\times 1000}{36}\\\\\text{Moles of }Ca(OH)_2=\frac{0.011\times 36}{1000}=0.0004mol$

1 mole of calcium hydroxide produces 1 mole of calcium ions and 2 moles of hydroxide ions.

Moles of hydroxide ions = (0.0004 × 2) = 0.0008 moles

Hence, the moles of hydroxide ions present in the sample is 0.0008 moles

8 0

3 years ago

Which is true about all the different types of matter?

Marat540 [252]

Answer: 1. It is made up of the same basic particles

Matter is made up of atoms, molecules, and ions that cause it to have mass and volume. The different types of matter are made up of the same basic particles but differ on the molecular arrangement and energy the atoms contains that's why they appear differently and have different properties.

8 0

3 years ago