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3 years ago

5) answer is A

Chemistry

1 answer:

Burka [1]3 years ago

3 0

Answer:

A) positive; added

Explanation:

Based on the reaction:

2NaHCO3(s) + 129kJ → Na2CO3(s) + H2(g) + CO2(g)

2 moles of NaHCO3 requires 129kJ to produce 1 mole of Na2CO3, 1 mole of H2 and 1 mole of CO2.

That means, the energy must be added being, thus, an exothermic reaction. The exothermic reactions have ΔH >0.

Thus, right answer is:

A) positive; added

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An aqueous CsCl solution is 8.00 wt% CsCl and has a density of 1.0643 g/mL at 20°C. What is the boiling point of this solution?

umka2103 [35]

Answer: The boiling point of solution is 100.53

Explanation:

We are given:

8.00 wt % of CsCl

This means that 8.00 grams of CsCl is present in 100 grams of solution

Mass of solvent = (100 - 8) g = 92 grams

The equation used to calculate elevation in boiling point follows:

$\Delta T_b=\text{Boiling point of solution}-\text{Boiling point of pure solution}$

To calculate the elevation in boiling point, we use the equation:

$\Delta T_b=iK_bm$

Or,

$\text{Boiling point of solution}-\text{Boiling point of pure solution}=i\times K_b\times \frac{m_{solute}\times 1000}{M_{solute}\times W_{solvent}\text{ (in grams)}}$

where,

Boiling point of pure solution = 100°C

i = Vant hoff factor = 2 (For CsCl)

$K_b$ = molal boiling point elevation constant = 0.51°C/m

$m_{solute}$ = Given mass of solute (CsCl) = 8.00 g

$M_{solute}$ = Molar mass of solute (CsCl) = 168.4 g/mol

$W_{solvent}$ = Mass of solvent (water) = 92 g

Putting values in above equation, we get:

$\text{Boiling point of solution}-100=2\times 0.51^oC/m\times \frac{8.00\times 1000}{168.4g/mol\times 92}\\\\\text{Boiling point of solution}=100.53^oC$

Hence, the boiling point of solution is 100.53

6 0

3 years ago

A bus travels 20km in 30minutes what is the average speed of the bus?

Vera_Pavlovna [14]

Answer:

40km/hr

Explanation:

Speed = Distance ÷ Time and since they both have different units we have to change one of them. Therefore if we change 30 minutes to half an hour we say 20km ÷ ¹/2

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3 years ago

What is the ratio of [a–]/[ha] at ph 3.75? the pka of formic acid (methanoic acid, h–cooh) is 3.75?

Vikentia [17]

The formula for pH given the pKa and the concentrations are:

pH = pKa + log [a–]/[ha]

Therefore calculating:

3.75 = 3.75 + log [a–]/[ha]

log [a–]/[ha] = 0

[a–]/[ha] = 10^0

[a–]/[ha] = 1

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