Category: Chemistry

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A strain gauge, having a gauge factor of 2, is mounted on a rectangular steel bar (Em =200×10° kN/m2), as shown in Figure.

A strain gauge, having a gauge factor of 2, is mounted on a rectangular steel bar (Em =200×10° kN/m2), as shown in Figure. The bar is 3 cm wide and 1 cm high, and is subjected to a tensile force of 30 kN. The voltage input vFlOV. 1)

Determine the resistance change of the strain gauge if the resistance of the gauge was 1200 in the absence of the axial load.

In the Wheatstone bridge circuit, all the resistors are 120 52, and it is balanced without external forces;

2) If the measurement device is able to measure 0 to 100 kN. It is required to have a resolution of 1 kN, please determine the gain needed for a 12-bit ±.5V sampling device;

3) Suppose the strain gauge is to be connected to a measurement device capable of determining a change in resistance with a stated uncertainty of 0.005 52 (95%). What uncertainty in stress would result when using this resistance measurement device?

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Hỗn hợp E gồm hai triglixerit X và Y có tỉ lệ mol tương ứng là 2 : 3.

Hỗn hợp E gồm hai triglixerit X và Y có tỉ lệ mol tương ứng là 2 : 3. Xà phòng hóa hoàn toàn E bằng dung dịch NaOH dư, thu được hỗn hợp muối gồm C15H31COONa, C17H31COONa và C17H33COONa. Khi cho m gam E tác dụng với H2 dư (xúc tác Ni, t°) thì số mol H2 phản ứng tối đa là 0,07 mol. Mặt khác, đốt cháy hoàn toàn m gam E, thu được 2,65 mol CO2 và 2,48 mol H2O. Khối lượng của X trong m gam E là

A. 24,96 gam.

B. 16,60 gam.

C. 17,12 gam.

D. 16,12 gam.

ANSWER:  mX = 16,60 gam

Quy đổi E thành (HCOO)3C3H5 (a), CH2 (b), H2 (-0,07)

nCO2 = 6a + b = 2,65

nH2O = 4a + b – 0,07 = 2,48

—> a = 0,05; b = 2,35

—> nX = 0,02 và nY = 0,03

Dễ thấy nH2 = 2nX + nY nên:

X là (C17H31COO)(C15H31COO)2C3H5

Y là (C17H33COO)(C15H31COO)2C3H5

—> mX = 16,60 gam

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A box of spherical candies is 23 g and its volume is 32.3 cm^3.

A box of spherical candies is 23 g and its volume is 32.3 cm^3.

If the average mass of a single jawbreaker is 0.94g, what is the radius of a single jawbreaker?

ANSWER:

The radius of each jawbreaker is approximately 0.68 cm.

Volume of a sphere;

  • v = 4 /3 πr³

where

r = radius

Therefore,

 

23 g  = 32.3 cm³

0.94 g  = ?

cross multiply

volume of a single jawbreaker = 32.3 × 0.94 / 23 = 30.362 / 23 = 1.32 cm³

Therefore,

volume of each jawbreaker = 4 /3 πr³

1.32 = 4 / 3 × 3.14 × r³

r³ = 1.32 /4.18666666667

r³ = 0.31533683707

r = ∛0.31533683707

r = 0.680651651 = 0.68

Therefore, the radius of each jawbreaker is approximately 0.68 cm.