8. A student filled a graduated cylinder with water and read the meniscus at 25.8 mL. The student

Chemistry

1 answer:

fomenos3 years ago

5 0

Answer:

Explanation:

The mass of a substance when given the density and volume can be found by using the formula

mass = Density × volume

volume = final volume of water - initial volume of water

From the question

volume = 35.9 ml - 25.8 ml = 10.1 mL

We have

mass = 2.99 × 10.1 = 30.199 g

We have the final answer as

Hope this helps you

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____ HBr + ____ Mg(OH)2 ---> ____ MgBr2 + ____ H2O

swat32

Hello Camkirkland,
I think that you are trying to balance this equation.
In order to balance a chemical equation, the numbers of atoms of each element must be equal on both sides of the equation.

In this particular equation, the answer would be (2) HBr + (1) Mg(OH)2 ---> (1) MgBr2 + (2) H2O.

Hope this answers your question!

4 0

3 years ago

What is the pH of a mixture of 0.042 M NaH2PO4 and 0.058 M Na2HPO4? Hint: The pKa of phosphate is 6.86.

AlekseyPX

Answer:

The pH value of the mixture will be 7.00

Explanation:

Mono and disodium hydrogen phosphate mixture act as a buffer to maintain pH value around 7. Henderson–Hasselbalch equation is used to determine the pH value of a buffer mixture, which is mathematically expressed as,

$pH=pK_{a} + log(\frac{[Base]}{[Acid]})$

According to the given conditions, the equation will become as follow

$pH=pK_{a} + log(\frac{[Na_{2}HPO_{4} ]}{[NaH_{2}PO_{4}]})$

The base and acid are assigned by observing the pKa values of both the compounds; smaller value means more acidic. NaH₂PO₄ has a pKa value of 6.86, while Na₂HPO₄ has a pKa value of 12.32 (not given, but it's a constant). Another more easy way is to the count the acidic hydrogen in the molecular formula; the compound with more acidic hydrogens will be assigned acidic and vice versa.

Placing all the given data we obtain,

$pH=6.86 + log(\frac{0.058}{0.042})$