Question 3(Multiple Choice Worth 3 points)

1. Convert 67500 mg to the unit hg

Mice21 [21]

Answer:

0.675

Explanation:

4 0

4 years ago

Given the atomic mass of select elements, calculate the molar mass of each salt. Element Molar mass (g/mol) Beryllium (Be) 9.012

jeka94

Answer:

1. 266.22 g/mol

2. 168.81 g/mol

3. 223.35 g/mol

4. 199.88 g/mol

Explanation:

For you to calculate the molar mass of the salt you need to sum the molar masses of every element in the salt.

In the first salt, PdBr $2_{123}$ , the subscript 2 means that there are 2 atoms of Br. So for you to calculate the molar mass of the salt you need to sum the molar mass of Pd and 2 times the molar mass of Br, as follows:

106 g/mol + 2(79.90 g/mol) = 266.22 g/mol

In the second salt BeBr $2_{123}$ there are 2 atoms of Br and 1 of Be, so the molar mass is:

9.012 g/mol +2(79.90 g/mol) = 186.22 g/mol

In the third salt CuBr $2_{123}$ there are 2 atoms of Br and 1 of Cu, so the molar mass is:

63.55 g/mol + 2(79.90 g/mol) = 223.35 g/mol

And in the fourth salt CaBr $2_{123}$ there are 2 atoms of Br and 1 of Ca, so the molar mass is:

40.08 g/mol + 2(79.90 g/mol) = 199.88 g/mol

6 0

3 years ago

Which particle has the least mass? Proton, a helium atom, electron, hydrogen atom

Tpy6a [65]

Answer:electron

Explanation:

3 0

3 years ago

A chemist needs 10 liters of a 25% acid solution. The solution is to be mixed from three solutions whose concentrations are 10%,

mojhsa [17]

Answer:

a) 1 litre of 10% solution and 7 litre of 20% solution

b) 1.67 litres of 50% solution and 8.33 litres of the 20% solution

c) 3.75 litres of 50% solution and 6.25 litres of 20% solution

Explanation:

Given:

chemist needs = 10 liters of a 25% acid solution

Concentration of three solutions that are to be mixed = 10%, 20% and 50%.

Solution:

A) Use 2 liters of the 50% solution

Let us mix this with 10% and 20% solution

They will have to equal 8 litres

Let x=20% solution

Then (8-x) =10%

So the equation becomes,

10%(8-x)+ 20%x+50%(2)=25(10)

(0.1)(8-x) +0.2x+0.50(2)= 0.25(10)

0.8-0.1x+0.2x+1.0=2.5

0.2x-0.1x=2.5-0.8-1.0

0.1x=0.7

$x=\frac{0.7}{0.1}$

x= 7

so, 8-x = 8 -7= 1 litre of 10% solution and 7 litre of 20% solution

B)Use as little as possible of the 50% solution

Let x be the amount of 50% solution.

Then(10-x) be the 20% solution

Now the equation becomes,

50%(x)+20%(10-x)=25%(10)

0.50x+0.2(10-x)=0.25(10)

0.5x+2.0-0.2x=2.5

0.3x=2.5-2.0

0.3x=0.5

$x=\frac{0.5}{0.3}$

x=1.67

now (10-x)=(10-1.67)=8.33

so there will be 1.67 litres of 50% solution and 8.33 litres of the 20% solution

c) ) Use as much as possible of the 50% solution

Let x be the amount of 50% solution.

Then(10-x) be the 20% solution

Now the equation becomes,

50%(x)+10%(10-x)=25%(10)

0.50x+0.1(10-x)=0.25(10)

0.5x+1.0-0.1x=2.5

0.4x=2.5-1.0

0.4x=1.5

$x=\frac{1.5}{0.3}$

x=3.75

Now, (10-x)=(10- 3.75)=6.26

So there will be 3.75 litres of 50% solution and 6.25 litres of 20% solution

5 0

3 years ago

Predict the spontaneity of a reaction (and the temperature dependence of the spontaneity) for each possible combination of signs

Akimi4 [234]

Answer and Explanation:

At constant pressure and constant temperature, the Gibbs free energy of a process is given by the following equation:

ΔG= ΔH - T ΔS

The process is spontaneous when ΔG<0. For this, there are four alternatives depending on the signs of ΔH and ΔS and the temperature (T):

1) ΔH negative, ΔS positive ⇒ b)The reaction will be spontaneous at all temperatures.

ΔG= (-H) - T (+S) ⇒ ΔG<0 always

2) ΔH positive, ΔS negative ⇒ c)The reaction will be nonspontaneous at all temperatures.

ΔG= (+H) - T (-S) ⇒ ΔG>0 always

3) ΔH negative, ΔS negative ⇒ d)The reaction will be spontaneous at low temperature, but nonspontaneous at high temperature.

ΔG= (-H) - T (-S) ⇒ ΔG<0 if TΔS is lower than ΔH, because is the positive term

4)ΔH positive, ΔS positive ⇒ a)The reaction will be nonspontaneous at low temperature, but spontaneous at high temperature.

ΔG= (+H) - T (+S) ⇒ ΔG<0 if TΔS higher than ΔH because is the negative term

8 0

3 years ago